 WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago  Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago WL#3817: Simplify string / memory area types and make things more consistent (first part)
The following type conversions was done:
- Changed byte to uchar
- Changed gptr to uchar*
- Change my_string to char *
- Change my_size_t to size_t
- Change size_s to size_t
Removed declaration of byte, gptr, my_string, my_size_t and size_s.
Following function parameter changes was done:
- All string functions in mysys/strings was changed to use size_t
instead of uint for string lengths.
- All read()/write() functions changed to use size_t (including vio).
- All protocoll functions changed to use size_t instead of uint
- Functions that used a pointer to a string length was changed to use size_t*
- Changed malloc(), free() and related functions from using gptr to use void *
as this requires fewer casts in the code and is more in line with how the
standard functions work.
- Added extra length argument to dirname_part() to return the length of the
created string.
- Changed (at least) following functions to take uchar* as argument:
- db_dump()
- my_net_write()
- net_write_command()
- net_store_data()
- DBUG_DUMP()
- decimal2bin() & bin2decimal()
- Changed my_compress() and my_uncompress() to use size_t. Changed one
argument to my_uncompress() from a pointer to a value as we only return
one value (makes function easier to use).
- Changed type of 'pack_data' argument to packfrm() to avoid casts.
- Changed in readfrm() and writefrom(), ha_discover and handler::discover()
the type for argument 'frmdata' to uchar** to avoid casts.
- Changed most Field functions to use uchar* instead of char* (reduced a lot of
casts).
- Changed field->val_xxx(xxx, new_ptr) to take const pointers.
Other changes:
- Removed a lot of not needed casts
- Added a few new cast required by other changes
- Added some cast to my_multi_malloc() arguments for safety (as string lengths
needs to be uint, not size_t).
- Fixed all calls to hash-get-key functions to use size_t*. (Needed to be done
explicitely as this conflict was often hided by casting the function to
hash_get_key).
- Changed some buffers to memory regions to uchar* to avoid casts.
- Changed some string lengths from uint to size_t.
- Changed field->ptr to be uchar* instead of char*. This allowed us to
get rid of a lot of casts.
- Some changes from true -> TRUE, false -> FALSE, unsigned char -> uchar
- Include zlib.h in some files as we needed declaration of crc32()
- Changed MY_FILE_ERROR to be (size_t) -1.
- Changed many variables to hold the result of my_read() / my_write() to be
size_t. This was needed to properly detect errors (which are
returned as (size_t) -1).
- Removed some very old VMS code
- Changed packfrm()/unpackfrm() to not be depending on uint size
(portability fix)
- Removed windows specific code to restore cursor position as this
causes slowdown on windows and we should not mix read() and pread()
calls anyway as this is not thread safe. Updated function comment to
reflect this. Changed function that depended on original behavior of
my_pwrite() to itself restore the cursor position (one such case).
- Added some missing checking of return value of malloc().
- Changed definition of MOD_PAD_CHAR_TO_FULL_LENGTH to avoid 'long' overflow.
- Changed type of table_def::m_size from my_size_t to ulong to reflect that
m_size is the number of elements in the array, not a string/memory
length.
- Moved THD::max_row_length() to table.cc (as it's not depending on THD).
Inlined max_row_length_blob() into this function.
- More function comments
- Fixed some compiler warnings when compiled without partitions.
- Removed setting of LEX_STRING() arguments in declaration (portability fix).
- Some trivial indentation/variable name changes.
- Some trivial code simplifications:
- Replaced some calls to alloc_root + memcpy to use
strmake_root()/strdup_root().
- Changed some calls from memdup() to strmake() (Safety fix)
- Simpler loops in client-simple.c
19 years ago Bug#34043: Server loops excessively in _checkchunk() when safemalloc is enabled
Essentially, the problem is that safemalloc is excruciatingly
slow as it checks all allocated blocks for overrun at each
memory management primitive, yielding a almost exponential
slowdown for the memory management functions (malloc, realloc,
free). The overrun check basically consists of verifying some
bytes of a block for certain magic keys, which catches some
simple forms of overrun. Another minor problem is violation
of aliasing rules and that its own internal list of blocks
is prone to corruption.
Another issue with safemalloc is rather the maintenance cost
as the tool has a significant impact on the server code.
Given the magnitude of memory debuggers available nowadays,
especially those that are provided with the platform malloc
implementation, maintenance of a in-house and largely obsolete
memory debugger becomes a burden that is not worth the effort
due to its slowness and lack of support for detecting more
common forms of heap corruption.
Since there are third-party tools that can provide the same
functionality at a lower or comparable performance cost, the
solution is to simply remove safemalloc. Third-party tools
can provide the same functionality at a lower or comparable
performance cost.
The removal of safemalloc also allows a simplification of the
malloc wrappers, removing quite a bit of kludge: redefinition
of my_malloc, my_free and the removal of the unused second
argument of my_free. Since free() always check whether the
supplied pointer is null, redudant checks are also removed.
Also, this patch adds unit testing for my_malloc and moves
my_realloc implementation into the same file as the other
memory allocation primitives. 16 years ago |
|
/* Copyright (C) 2000 MySQL AB, 2008-2009 Sun Microsystems, Inc
This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
/**
@file These functions handle keyblock cacheing for ISAM and MyISAM tables.
One cache can handle many files. It must contain buffers of the same blocksize. init_key_cache() should be used to init cache handler.
The free list (free_block_list) is a stack like structure. When a block is freed by free_block(), it is pushed onto the stack. When a new block is required it is first tried to pop one from the stack. If the stack is empty, it is tried to get a never-used block from the pool. If this is empty too, then a block is taken from the LRU ring, flushing it to disk, if neccessary. This is handled in find_key_block(). With the new free list, the blocks can have three temperatures: hot, warm and cold (which is free). This is remembered in the block header by the enum BLOCK_TEMPERATURE temperature variable. Remembering the temperature is neccessary to correctly count the number of warm blocks, which is required to decide when blocks are allowed to become hot. Whenever a block is inserted to another (sub-)chain, we take the old and new temperature into account to decide if we got one more or less warm block. blocks_unused is the sum of never used blocks in the pool and of currently free blocks. blocks_used is the number of blocks fetched from the pool and as such gives the maximum number of in-use blocks at any time.*/
/*
Key Cache Locking =================
All key cache locking is done with a single mutex per key cache: keycache->cache_lock. This mutex is locked almost all the time when executing code in this file (mf_keycache.c). However it is released for I/O and some copy operations.
The cache_lock is also released when waiting for some event. Waiting and signalling is done via condition variables. In most cases the thread waits on its thread->suspend condition variable. Every thread has a my_thread_var structure, which contains this variable and a '*next' and '**prev' pointer. These pointers are used to insert the thread into a wait queue.
A thread can wait for one block and thus be in one wait queue at a time only.
Before starting to wait on its condition variable with mysql_cond_wait(), the thread enters itself to a specific wait queue with link_into_queue() (double linked with '*next' + '**prev') or wait_on_queue() (single linked with '*next').
Another thread, when releasing a resource, looks up the waiting thread in the related wait queue. It sends a signal with mysql_cond_signal() to the waiting thread.
NOTE: Depending on the particular wait situation, either the sending thread removes the waiting thread from the wait queue with unlink_from_queue() or release_whole_queue() respectively, or the waiting thread removes itself.
There is one exception from this locking scheme when one thread wants to reuse a block for some other address. This works by first marking the block reserved (status= BLOCK_IN_SWITCH) and then waiting for all threads that are reading the block to finish. Each block has a reference to a condition variable (condvar). It holds a reference to the thread->suspend condition variable for the waiting thread (if such a thread exists). When that thread is signaled, the reference is cleared. The number of readers of a block is registered in block->hash_link->requests. See wait_for_readers() / remove_reader() for details. This is similar to the above, but it clearly means that only one thread can wait for a particular block. There is no queue in this case. Strangely enough block->convar is used for waiting for the assigned hash_link only. More precisely it is used to wait for all requests to be unregistered from the assigned hash_link.
The resize_queue serves two purposes: 1. Threads that want to do a resize wait there if in_resize is set. This is not used in the server. The server refuses a second resize request if one is already active. keycache->in_init is used for the synchronization. See set_var.cc. 2. Threads that want to access blocks during resize wait here during the re-initialization phase. When the resize is done, all threads on the queue are signalled. Hypothetical resizers can compete for resizing, and read/write requests will restart to request blocks from the freshly resized cache. If the cache has been resized too small, it is disabled and 'can_be_used' is false. In this case read/write requests bypass the cache. Since they increment and decrement 'cnt_for_resize_op', the next resizer can wait on the queue 'waiting_for_resize_cnt' until all I/O finished.*/
#include "mysys_priv.h"
#include "mysys_err.h"
#include <keycache.h>
#include "my_static.h"
#include <m_string.h>
#include <my_bit.h>
#include <errno.h>
#include <stdarg.h>
#include "probes_mysql.h"
/*
Some compilation flags have been added specifically for this module to control the following: - not to let a thread to yield the control when reading directly from key cache, which might improve performance in many cases; to enable this add: #define SERIALIZED_READ_FROM_CACHE
- to set an upper bound for number of threads simultaneously using the key cache; this setting helps to determine an optimal size for hash table and improve performance when the number of blocks in the key cache much less than the number of threads accessing it; to set this number equal to <N> add #define MAX_THREADS <N>
- to substitute calls of mysql_cond_wait for calls of mysql_cond_timedwait (wait with timeout set up); this setting should be used only when you want to trap a deadlock situation, which theoretically should not happen; to set timeout equal to <T> seconds add #define KEYCACHE_TIMEOUT <T>
- to enable the module traps and to send debug information from key cache module to a special debug log add: #define KEYCACHE_DEBUG
the name of this debug log file <LOG NAME> can be set through: #define KEYCACHE_DEBUG_LOG <LOG NAME>
if the name is not defined, it's set by default; if the KEYCACHE_DEBUG flag is not set up and we are in a debug mode, i.e. when ! defined(DBUG_OFF), the debug information from the module is sent to the regular debug log.
Example of the settings: #define SERIALIZED_READ_FROM_CACHE
#define MAX_THREADS 100
#define KEYCACHE_TIMEOUT 1
#define KEYCACHE_DEBUG
#define KEYCACHE_DEBUG_LOG "my_key_cache_debug.log"
*/
#define STRUCT_PTR(TYPE, MEMBER, a) \
(TYPE *) ((char *) (a) - offsetof(TYPE, MEMBER))
/* types of condition variables */#define COND_FOR_REQUESTED 0
#define COND_FOR_SAVED 1
#define COND_FOR_READERS 2
typedef mysql_cond_t KEYCACHE_CONDVAR;
/* descriptor of the page in the key cache block buffer */struct st_keycache_page{ int file; /* file to which the page belongs to */ my_off_t filepos; /* position of the page in the file */};
/* element in the chain of a hash table bucket */struct st_hash_link{ struct st_hash_link *next, **prev; /* to connect links in the same bucket */ struct st_block_link *block; /* reference to the block for the page: */ File file; /* from such a file */ my_off_t diskpos; /* with such an offset */ uint requests; /* number of requests for the page */};
/* simple states of a block */#define BLOCK_ERROR 1 /* an error occured when performing file i/o */
#define BLOCK_READ 2 /* file block is in the block buffer */
#define BLOCK_IN_SWITCH 4 /* block is preparing to read new page */
#define BLOCK_REASSIGNED 8 /* blk does not accept requests for old page */
#define BLOCK_IN_FLUSH 16 /* block is selected for flush */
#define BLOCK_CHANGED 32 /* block buffer contains a dirty page */
#define BLOCK_IN_USE 64 /* block is not free */
#define BLOCK_IN_EVICTION 128 /* block is selected for eviction */
#define BLOCK_IN_FLUSHWRITE 256 /* block is in write to file */
#define BLOCK_FOR_UPDATE 512 /* block is selected for buffer modification */
/* page status, returned by find_key_block */#define PAGE_READ 0
#define PAGE_TO_BE_READ 1
#define PAGE_WAIT_TO_BE_READ 2
/* block temperature determines in which (sub-)chain the block currently is */enum BLOCK_TEMPERATURE { BLOCK_COLD /*free*/ , BLOCK_WARM , BLOCK_HOT };
/* key cache block */struct st_block_link{ struct st_block_link *next_used, **prev_used; /* to connect links in the LRU chain (ring) */ struct st_block_link *next_changed, **prev_changed; /* for lists of file dirty/clean blocks */ struct st_hash_link *hash_link; /* backward ptr to referring hash_link */ KEYCACHE_WQUEUE wqueue[2]; /* queues on waiting requests for new/old pages */ uint requests; /* number of requests for the block */ uchar *buffer; /* buffer for the block page */ uint offset; /* beginning of modified data in the buffer */ uint length; /* end of data in the buffer */ uint status; /* state of the block */ enum BLOCK_TEMPERATURE temperature; /* block temperature: cold, warm, hot */ uint hits_left; /* number of hits left until promotion */ ulonglong last_hit_time; /* timestamp of the last hit */ KEYCACHE_CONDVAR *condvar; /* condition variable for 'no readers' event */};
KEY_CACHE dflt_key_cache_var;KEY_CACHE *dflt_key_cache= &dflt_key_cache_var;
#define FLUSH_CACHE 2000 /* sort this many blocks at once */
static int flush_all_key_blocks(KEY_CACHE *keycache);#ifdef THREAD
static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, mysql_mutex_t *mutex);static void release_whole_queue(KEYCACHE_WQUEUE *wqueue);#else
#define wait_on_queue(wqueue, mutex) do {} while (0)
#define release_whole_queue(wqueue) do {} while (0)
#endif
static void free_block(KEY_CACHE *keycache, BLOCK_LINK *block);#if !defined(DBUG_OFF)
static void test_key_cache(KEY_CACHE *keycache, const char *where, my_bool lock);#endif
#define KEYCACHE_HASH(f, pos) \
(((ulong) ((pos) / keycache->key_cache_block_size) + \ (ulong) (f)) & (keycache->hash_entries-1))#define FILE_HASH(f) ((uint) (f) & (CHANGED_BLOCKS_HASH-1))
#define DEFAULT_KEYCACHE_DEBUG_LOG "keycache_debug.log"
#if defined(KEYCACHE_DEBUG) && ! defined(KEYCACHE_DEBUG_LOG)
#define KEYCACHE_DEBUG_LOG DEFAULT_KEYCACHE_DEBUG_LOG
#endif
#if defined(KEYCACHE_DEBUG_LOG)
static FILE *keycache_debug_log=NULL;static void keycache_debug_print(const char *fmt,...);#define KEYCACHE_DEBUG_OPEN \
if (!keycache_debug_log) \ { \ keycache_debug_log= fopen(KEYCACHE_DEBUG_LOG, "w"); \ (void) setvbuf(keycache_debug_log, NULL, _IOLBF, BUFSIZ); \ }
#define KEYCACHE_DEBUG_CLOSE \
if (keycache_debug_log) \ { \ fclose(keycache_debug_log); \ keycache_debug_log= 0; \ }#else
#define KEYCACHE_DEBUG_OPEN
#define KEYCACHE_DEBUG_CLOSE
#endif /* defined(KEYCACHE_DEBUG_LOG) */
#if defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG)
#define KEYCACHE_DBUG_PRINT(l, m) \
{ if (keycache_debug_log) fprintf(keycache_debug_log, "%s: ", l); \ keycache_debug_print m; }
#define KEYCACHE_DBUG_ASSERT(a) \
{ if (! (a) && keycache_debug_log) fclose(keycache_debug_log); \ assert(a); }#else
#define KEYCACHE_DBUG_PRINT(l, m) DBUG_PRINT(l, m)
#define KEYCACHE_DBUG_ASSERT(a) DBUG_ASSERT(a)
#endif /* defined(KEYCACHE_DEBUG_LOG) && defined(KEYCACHE_DEBUG) */
#if defined(KEYCACHE_DEBUG) || !defined(DBUG_OFF)
#ifdef THREAD
static long keycache_thread_id;#define KEYCACHE_THREAD_TRACE(l) \
KEYCACHE_DBUG_PRINT(l,("|thread %ld",keycache_thread_id))
#define KEYCACHE_THREAD_TRACE_BEGIN(l) \
{ struct st_my_thread_var *thread_var= my_thread_var; \ keycache_thread_id= thread_var->id; \ KEYCACHE_DBUG_PRINT(l,("[thread %ld",keycache_thread_id)) }
#define KEYCACHE_THREAD_TRACE_END(l) \
KEYCACHE_DBUG_PRINT(l,("]thread %ld",keycache_thread_id))#else /* THREAD */
#define KEYCACHE_THREAD_TRACE(l) KEYCACHE_DBUG_PRINT(l,(""))
#define KEYCACHE_THREAD_TRACE_BEGIN(l) KEYCACHE_DBUG_PRINT(l,(""))
#define KEYCACHE_THREAD_TRACE_END(l) KEYCACHE_DBUG_PRINT(l,(""))
#endif /* THREAD */
#else
#define KEYCACHE_THREAD_TRACE_BEGIN(l)
#define KEYCACHE_THREAD_TRACE_END(l)
#define KEYCACHE_THREAD_TRACE(l)
#endif /* defined(KEYCACHE_DEBUG) || !defined(DBUG_OFF) */
#define BLOCK_NUMBER(b) \
((uint) (((char*)(b)-(char *) keycache->block_root)/sizeof(BLOCK_LINK)))#define HASH_LINK_NUMBER(h) \
((uint) (((char*)(h)-(char *) keycache->hash_link_root)/sizeof(HASH_LINK)))
#if (defined(KEYCACHE_TIMEOUT) && !defined(__WIN__)) || defined(KEYCACHE_DEBUG)
static int keycache_pthread_cond_wait(mysql_cond_t *cond, mysql_mutex_t *mutex);#else
#define keycache_pthread_cond_wait(C, M) mysql_cond_wait(C, M)
#endif
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex);static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex);static int keycache_pthread_cond_signal(mysql_cond_t *cond);#else
#define keycache_pthread_mutex_lock(M) mysql_mutex_lock(M)
#define keycache_pthread_mutex_unlock(M) mysql_mutex_unlock(M)
#define keycache_pthread_cond_signal(C) mysql_cond_signal(C)
#endif /* defined(KEYCACHE_DEBUG) */
#if !defined(DBUG_OFF)
#if defined(inline)
#undef inline
#endif
#define inline /* disabled inline for easier debugging */
static int fail_block(BLOCK_LINK *block);static int fail_hlink(HASH_LINK *hlink);static int cache_empty(KEY_CACHE *keycache);#endif
static inline uint next_power(uint value){ return (uint) my_round_up_to_next_power((uint32) value) << 1;}
/*
Initialize a key cache
SYNOPSIS init_key_cache() keycache pointer to a key cache data structure key_cache_block_size size of blocks to keep cached data use_mem total memory to use for the key cache division_limit division limit (may be zero) age_threshold age threshold (may be zero)
RETURN VALUE number of blocks in the key cache, if successful, 0 - otherwise.
NOTES. if keycache->key_cache_inited != 0 we assume that the key cache is already initialized. This is for now used by myisamchk, but shouldn't be something that a program should rely on!
It's assumed that no two threads call this function simultaneously referring to the same key cache handle.
*/
int init_key_cache(KEY_CACHE *keycache, uint key_cache_block_size, size_t use_mem, uint division_limit, uint age_threshold){ ulong blocks, hash_links; size_t length; int error; DBUG_ENTER("init_key_cache"); DBUG_ASSERT(key_cache_block_size >= 512);
KEYCACHE_DEBUG_OPEN; if (keycache->key_cache_inited && keycache->disk_blocks > 0) { DBUG_PRINT("warning",("key cache already in use")); DBUG_RETURN(0); }
keycache->global_cache_w_requests= keycache->global_cache_r_requests= 0; keycache->global_cache_read= keycache->global_cache_write= 0; keycache->disk_blocks= -1; if (! keycache->key_cache_inited) { keycache->key_cache_inited= 1; /*
Initialize these variables once only. Their value must survive re-initialization during resizing. */ keycache->in_resize= 0; keycache->resize_in_flush= 0; keycache->cnt_for_resize_op= 0; keycache->waiting_for_resize_cnt.last_thread= NULL; keycache->in_init= 0; mysql_mutex_init(key_KEY_CACHE_cache_lock, &keycache->cache_lock, MY_MUTEX_INIT_FAST); keycache->resize_queue.last_thread= NULL; }
keycache->key_cache_mem_size= use_mem; keycache->key_cache_block_size= key_cache_block_size; DBUG_PRINT("info", ("key_cache_block_size: %u", key_cache_block_size));
blocks= (ulong) (use_mem / (sizeof(BLOCK_LINK) + 2 * sizeof(HASH_LINK) + sizeof(HASH_LINK*) * 5/4 + key_cache_block_size)); /* It doesn't make sense to have too few blocks (less than 8) */ if (blocks >= 8) { for ( ; ; ) { /* Set my_hash_entries to the next bigger 2 power */ if ((keycache->hash_entries= next_power(blocks)) < blocks * 5/4) keycache->hash_entries<<= 1; hash_links= 2 * blocks;#if defined(MAX_THREADS)
if (hash_links < MAX_THREADS + blocks - 1) hash_links= MAX_THREADS + blocks - 1;#endif
while ((length= (ALIGN_SIZE(blocks * sizeof(BLOCK_LINK)) + ALIGN_SIZE(hash_links * sizeof(HASH_LINK)) + ALIGN_SIZE(sizeof(HASH_LINK*) * keycache->hash_entries))) + ((size_t) blocks * keycache->key_cache_block_size) > use_mem) blocks--; /* Allocate memory for cache page buffers */ if ((keycache->block_mem= my_large_malloc((size_t) blocks * keycache->key_cache_block_size, MYF(0)))) { /*
Allocate memory for blocks, hash_links and hash entries; For each block 2 hash links are allocated */ if ((keycache->block_root= (BLOCK_LINK*) my_malloc(length, MYF(0)))) break; my_large_free(keycache->block_mem); keycache->block_mem= 0; } if (blocks < 8) { my_errno= ENOMEM; my_error(EE_OUTOFMEMORY, MYF(0), blocks * keycache->key_cache_block_size); goto err; } blocks= blocks / 4*3; } keycache->blocks_unused= blocks; keycache->disk_blocks= (int) blocks; keycache->hash_links= hash_links; keycache->hash_root= (HASH_LINK**) ((char*) keycache->block_root + ALIGN_SIZE(blocks*sizeof(BLOCK_LINK))); keycache->hash_link_root= (HASH_LINK*) ((char*) keycache->hash_root + ALIGN_SIZE((sizeof(HASH_LINK*) * keycache->hash_entries))); bzero((uchar*) keycache->block_root, keycache->disk_blocks * sizeof(BLOCK_LINK)); bzero((uchar*) keycache->hash_root, keycache->hash_entries * sizeof(HASH_LINK*)); bzero((uchar*) keycache->hash_link_root, keycache->hash_links * sizeof(HASH_LINK)); keycache->hash_links_used= 0; keycache->free_hash_list= NULL; keycache->blocks_used= keycache->blocks_changed= 0;
keycache->global_blocks_changed= 0; keycache->blocks_available=0; /* For debugging */
/* The LRU chain is empty after initialization */ keycache->used_last= NULL; keycache->used_ins= NULL; keycache->free_block_list= NULL; keycache->keycache_time= 0; keycache->warm_blocks= 0; keycache->min_warm_blocks= (division_limit ? blocks * division_limit / 100 + 1 : blocks); keycache->age_threshold= (age_threshold ? blocks * age_threshold / 100 : blocks);
keycache->can_be_used= 1;
keycache->waiting_for_hash_link.last_thread= NULL; keycache->waiting_for_block.last_thread= NULL; DBUG_PRINT("exit", ("disk_blocks: %d block_root: 0x%lx hash_entries: %d\
hash_root: 0x%lx hash_links: %d hash_link_root: 0x%lx", keycache->disk_blocks, (long) keycache->block_root, keycache->hash_entries, (long) keycache->hash_root, keycache->hash_links, (long) keycache->hash_link_root)); bzero((uchar*) keycache->changed_blocks, sizeof(keycache->changed_blocks[0]) * CHANGED_BLOCKS_HASH); bzero((uchar*) keycache->file_blocks, sizeof(keycache->file_blocks[0]) * CHANGED_BLOCKS_HASH); } else { /* key_buffer_size is specified too small. Disable the cache. */ keycache->can_be_used= 0; }
keycache->blocks= keycache->disk_blocks > 0 ? keycache->disk_blocks : 0; DBUG_RETURN((int) keycache->disk_blocks);
err: error= my_errno; keycache->disk_blocks= 0; keycache->blocks= 0; if (keycache->block_mem) { my_large_free((uchar*) keycache->block_mem); keycache->block_mem= NULL; } if (keycache->block_root) { my_free(keycache->block_root); keycache->block_root= NULL; } my_errno= error; keycache->can_be_used= 0; DBUG_RETURN(0);}
/*
Resize a key cache
SYNOPSIS resize_key_cache() keycache pointer to a key cache data structure key_cache_block_size size of blocks to keep cached data use_mem total memory to use for the new key cache division_limit new division limit (if not zero) age_threshold new age threshold (if not zero)
RETURN VALUE number of blocks in the key cache, if successful, 0 - otherwise.
NOTES. The function first compares the memory size and the block size parameters with the key cache values.
If they differ the function free the the memory allocated for the old key cache blocks by calling the end_key_cache function and then rebuilds the key cache with new blocks by calling init_key_cache.
The function starts the operation only when all other threads performing operations with the key cache let her to proceed (when cnt_for_resize=0).*/
int resize_key_cache(KEY_CACHE *keycache, uint key_cache_block_size, size_t use_mem, uint division_limit, uint age_threshold){ int blocks; DBUG_ENTER("resize_key_cache");
if (!keycache->key_cache_inited) DBUG_RETURN(keycache->disk_blocks);
if(key_cache_block_size == keycache->key_cache_block_size && use_mem == keycache->key_cache_mem_size) { change_key_cache_param(keycache, division_limit, age_threshold); DBUG_RETURN(keycache->disk_blocks); }
keycache_pthread_mutex_lock(&keycache->cache_lock);
#ifdef THREAD
/*
We may need to wait for another thread which is doing a resize already. This cannot happen in the MySQL server though. It allows one resizer only. In set_var.cc keycache->in_init is used to block multiple attempts. */ while (keycache->in_resize) { /* purecov: begin inspected */ wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); /* purecov: end */ }#endif
/*
Mark the operation in progress. This blocks other threads from doing a resize in parallel. It prohibits new blocks to enter the cache. Read/write requests can bypass the cache during the flush phase. */ keycache->in_resize= 1;
/* Need to flush only if keycache is enabled. */ if (keycache->can_be_used) { /* Start the flush phase. */ keycache->resize_in_flush= 1;
if (flush_all_key_blocks(keycache)) { /* TODO: if this happens, we should write a warning in the log file ! */ keycache->resize_in_flush= 0; blocks= 0; keycache->can_be_used= 0; goto finish; } DBUG_ASSERT(cache_empty(keycache));
/* End the flush phase. */ keycache->resize_in_flush= 0; }
#ifdef THREAD
/*
Some direct read/write operations (bypassing the cache) may still be unfinished. Wait until they are done. If the key cache can be used, direct I/O is done in increments of key_cache_block_size. That is, every block is checked if it is in the cache. We need to wait for pending I/O before re-initializing the cache, because we may change the block size. Otherwise they could check for blocks at file positions where the new block division has none. We do also want to wait for I/O done when (if) the cache was disabled. It must not run in parallel with normal cache operation. */ while (keycache->cnt_for_resize_op) wait_on_queue(&keycache->waiting_for_resize_cnt, &keycache->cache_lock);#else
KEYCACHE_DBUG_ASSERT(keycache->cnt_for_resize_op == 0);#endif
/*
Free old cache structures, allocate new structures, and initialize them. Note that the cache_lock mutex and the resize_queue are left untouched. We do not lose the cache_lock and will release it only at the end of this function. */ end_key_cache(keycache, 0); /* Don't free mutex */ /* The following will work even if use_mem is 0 */ blocks= init_key_cache(keycache, key_cache_block_size, use_mem, division_limit, age_threshold);
finish: /*
Mark the resize finished. This allows other threads to start a resize or to request new cache blocks. */ keycache->in_resize= 0;
/* Signal waiting threads. */ release_whole_queue(&keycache->resize_queue);
keycache_pthread_mutex_unlock(&keycache->cache_lock); DBUG_RETURN(blocks);}
/*
Increment counter blocking resize key cache operation*/static inline void inc_counter_for_resize_op(KEY_CACHE *keycache){ keycache->cnt_for_resize_op++;}
/*
Decrement counter blocking resize key cache operation; Signal the operation to proceed when counter becomes equal zero*/static inline void dec_counter_for_resize_op(KEY_CACHE *keycache){ if (!--keycache->cnt_for_resize_op) release_whole_queue(&keycache->waiting_for_resize_cnt);}
/*
Change the key cache parameters
SYNOPSIS change_key_cache_param() keycache pointer to a key cache data structure division_limit new division limit (if not zero) age_threshold new age threshold (if not zero)
RETURN VALUE none
NOTES. Presently the function resets the key cache parameters concerning midpoint insertion strategy - division_limit and age_threshold.*/
void change_key_cache_param(KEY_CACHE *keycache, uint division_limit, uint age_threshold){ DBUG_ENTER("change_key_cache_param");
keycache_pthread_mutex_lock(&keycache->cache_lock); if (division_limit) keycache->min_warm_blocks= (keycache->disk_blocks * division_limit / 100 + 1); if (age_threshold) keycache->age_threshold= (keycache->disk_blocks * age_threshold / 100); keycache_pthread_mutex_unlock(&keycache->cache_lock); DBUG_VOID_RETURN;}
/*
Remove key_cache from memory
SYNOPSIS end_key_cache() keycache key cache handle cleanup Complete free (Free also mutex for key cache)
RETURN VALUE none*/
void end_key_cache(KEY_CACHE *keycache, my_bool cleanup){ DBUG_ENTER("end_key_cache"); DBUG_PRINT("enter", ("key_cache: 0x%lx", (long) keycache));
if (!keycache->key_cache_inited) DBUG_VOID_RETURN;
if (keycache->disk_blocks > 0) { if (keycache->block_mem) { my_large_free((uchar*) keycache->block_mem); keycache->block_mem= NULL; my_free(keycache->block_root); keycache->block_root= NULL; } keycache->disk_blocks= -1; /* Reset blocks_changed to be safe if flush_all_key_blocks is called */ keycache->blocks_changed= 0; }
DBUG_PRINT("status", ("used: %lu changed: %lu w_requests: %lu " "writes: %lu r_requests: %lu reads: %lu", keycache->blocks_used, keycache->global_blocks_changed, (ulong) keycache->global_cache_w_requests, (ulong) keycache->global_cache_write, (ulong) keycache->global_cache_r_requests, (ulong) keycache->global_cache_read));
/*
Reset these values to be able to detect a disabled key cache. See Bug#44068 (RESTORE can disable the MyISAM Key Cache). */ keycache->blocks_used= 0; keycache->blocks_unused= 0;
if (cleanup) { mysql_mutex_destroy(&keycache->cache_lock); keycache->key_cache_inited= keycache->can_be_used= 0; KEYCACHE_DEBUG_CLOSE; } DBUG_VOID_RETURN;} /* end_key_cache */
#ifdef THREAD
/*
Link a thread into double-linked queue of waiting threads.
SYNOPSIS link_into_queue() wqueue pointer to the queue structure thread pointer to the thread to be added to the queue
RETURN VALUE none
NOTES. Queue is represented by a circular list of the thread structures The list is double-linked of the type (**prev,*next), accessed by a pointer to the last element.*/
static void link_into_queue(KEYCACHE_WQUEUE *wqueue, struct st_my_thread_var *thread){ struct st_my_thread_var *last;
DBUG_ASSERT(!thread->next && !thread->prev); if (! (last= wqueue->last_thread)) { /* Queue is empty */ thread->next= thread; thread->prev= &thread->next; } else { thread->prev= last->next->prev; last->next->prev= &thread->next; thread->next= last->next; last->next= thread; } wqueue->last_thread= thread;}
/*
Unlink a thread from double-linked queue of waiting threads
SYNOPSIS unlink_from_queue() wqueue pointer to the queue structure thread pointer to the thread to be removed from the queue
RETURN VALUE none
NOTES. See NOTES for link_into_queue*/
static void unlink_from_queue(KEYCACHE_WQUEUE *wqueue, struct st_my_thread_var *thread){ KEYCACHE_DBUG_PRINT("unlink_from_queue", ("thread %ld", thread->id)); DBUG_ASSERT(thread->next && thread->prev); if (thread->next == thread) /* The queue contains only one member */ wqueue->last_thread= NULL; else { thread->next->prev= thread->prev; *thread->prev=thread->next; if (wqueue->last_thread == thread) wqueue->last_thread= STRUCT_PTR(struct st_my_thread_var, next, thread->prev); } thread->next= NULL;#if !defined(DBUG_OFF)
/*
This makes it easier to see it's not in a chain during debugging. And some DBUG_ASSERT() rely on it. */ thread->prev= NULL;#endif
}
/*
Add a thread to single-linked queue of waiting threads
SYNOPSIS wait_on_queue() wqueue Pointer to the queue structure. mutex Cache_lock to acquire after awake.
RETURN VALUE none
NOTES. Queue is represented by a circular list of the thread structures The list is single-linked of the type (*next), accessed by a pointer to the last element.
The function protects against stray signals by verifying that the current thread is unlinked from the queue when awaking. However, since several threads can wait for the same event, it might be necessary for the caller of the function to check again if the condition for awake is indeed matched.*/
static void wait_on_queue(KEYCACHE_WQUEUE *wqueue, mysql_mutex_t *mutex){ struct st_my_thread_var *last; struct st_my_thread_var *thread= my_thread_var;
/* Add to queue. */ DBUG_ASSERT(!thread->next); DBUG_ASSERT(!thread->prev); /* Not required, but must be true anyway. */ if (! (last= wqueue->last_thread)) thread->next= thread; else { thread->next= last->next; last->next= thread; } wqueue->last_thread= thread;
/*
Wait until thread is removed from queue by the signalling thread. The loop protects against stray signals. */ do { KEYCACHE_DBUG_PRINT("wait", ("suspend thread %ld", thread->id)); keycache_pthread_cond_wait(&thread->suspend, mutex); } while (thread->next);}
/*
Remove all threads from queue signaling them to proceed
SYNOPSIS release_whole_queue() wqueue pointer to the queue structure
RETURN VALUE none
NOTES. See notes for wait_on_queue(). When removed from the queue each thread is signaled via condition variable thread->suspend.*/
static void release_whole_queue(KEYCACHE_WQUEUE *wqueue){ struct st_my_thread_var *last; struct st_my_thread_var *next; struct st_my_thread_var *thread;
/* Queue may be empty. */ if (!(last= wqueue->last_thread)) return;
next= last->next; do { thread=next; KEYCACHE_DBUG_PRINT("release_whole_queue: signal", ("thread %ld", thread->id)); /* Signal the thread. */ keycache_pthread_cond_signal(&thread->suspend); /* Take thread from queue. */ next=thread->next; thread->next= NULL; } while (thread != last);
/* Now queue is definitely empty. */ wqueue->last_thread= NULL;}
#endif /* THREAD */
/*
Unlink a block from the chain of dirty/clean blocks*/
static inline void unlink_changed(BLOCK_LINK *block){ DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); if (block->next_changed) block->next_changed->prev_changed= block->prev_changed; *block->prev_changed= block->next_changed;
#if !defined(DBUG_OFF)
/*
This makes it easier to see it's not in a chain during debugging. And some DBUG_ASSERT() rely on it. */ block->next_changed= NULL; block->prev_changed= NULL;#endif
}
/*
Link a block into the chain of dirty/clean blocks*/
static inline void link_changed(BLOCK_LINK *block, BLOCK_LINK **phead){ DBUG_ASSERT(!block->next_changed); DBUG_ASSERT(!block->prev_changed); block->prev_changed= phead; if ((block->next_changed= *phead)) (*phead)->prev_changed= &block->next_changed; *phead= block;}
/*
Link a block in a chain of clean blocks of a file.
SYNOPSIS link_to_file_list() keycache Key cache handle block Block to relink file File to be linked to unlink If to unlink first
DESCRIPTION Unlink a block from whichever chain it is linked in, if it's asked for, and link it to the chain of clean blocks of the specified file.
NOTE Please do never set/clear BLOCK_CHANGED outside of link_to_file_list() or link_to_changed_list(). You would risk to damage correct counting of changed blocks and to find blocks in the wrong hash.
RETURN void*/
static void link_to_file_list(KEY_CACHE *keycache, BLOCK_LINK *block, int file, my_bool unlink_block){ DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT(block->hash_link && block->hash_link->block == block); DBUG_ASSERT(block->hash_link->file == file); if (unlink_block) unlink_changed(block); link_changed(block, &keycache->file_blocks[FILE_HASH(file)]); if (block->status & BLOCK_CHANGED) { block->status&= ~BLOCK_CHANGED; keycache->blocks_changed--; keycache->global_blocks_changed--; }}
/*
Re-link a block from the clean chain to the dirty chain of a file.
SYNOPSIS link_to_changed_list() keycache key cache handle block block to relink
DESCRIPTION Unlink a block from the chain of clean blocks of a file and link it to the chain of dirty blocks of the same file.
NOTE Please do never set/clear BLOCK_CHANGED outside of link_to_file_list() or link_to_changed_list(). You would risk to damage correct counting of changed blocks and to find blocks in the wrong hash.
RETURN void*/
static void link_to_changed_list(KEY_CACHE *keycache, BLOCK_LINK *block){ DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); DBUG_ASSERT(block->hash_link && block->hash_link->block == block);
unlink_changed(block); link_changed(block, &keycache->changed_blocks[FILE_HASH(block->hash_link->file)]); block->status|=BLOCK_CHANGED; keycache->blocks_changed++; keycache->global_blocks_changed++;}
/*
Link a block to the LRU chain at the beginning or at the end of one of two parts.
SYNOPSIS link_block() keycache pointer to a key cache data structure block pointer to the block to link to the LRU chain hot <-> to link the block into the hot subchain at_end <-> to link the block at the end of the subchain
RETURN VALUE none
NOTES. The LRU ring is represented by a circular list of block structures. The list is double-linked of the type (**prev,*next) type. The LRU ring is divided into two parts - hot and warm. There are two pointers to access the last blocks of these two parts. The beginning of the warm part follows right after the end of the hot part. Only blocks of the warm part can be used for eviction. The first block from the beginning of this subchain is always taken for eviction (keycache->last_used->next)
LRU chain: +------+ H O T +------+ +----| end |----...<----| beg |----+ | +------+last +------+ | v<-link in latest hot (new end) | | link in latest warm (new end)->^ | +------+ W A R M +------+ | +----| beg |---->...----| end |----+ +------+ +------+ins first for eviction
It is also possible that the block is selected for eviction and thus not linked in the LRU ring.*/
static void link_block(KEY_CACHE *keycache, BLOCK_LINK *block, my_bool hot, my_bool at_end){ BLOCK_LINK *ins; BLOCK_LINK **pins;
DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ DBUG_ASSERT(!block->requests); DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); DBUG_ASSERT(!block->next_used); DBUG_ASSERT(!block->prev_used);#ifdef THREAD
if (!hot && keycache->waiting_for_block.last_thread) { /* Signal that in the LRU warm sub-chain an available block has appeared */ struct st_my_thread_var *last_thread= keycache->waiting_for_block.last_thread; struct st_my_thread_var *first_thread= last_thread->next; struct st_my_thread_var *next_thread= first_thread; HASH_LINK *hash_link= (HASH_LINK *) first_thread->opt_info; struct st_my_thread_var *thread; do { thread= next_thread; next_thread= thread->next; /*
We notify about the event all threads that ask for the same page as the first thread in the queue */ if ((HASH_LINK *) thread->opt_info == hash_link) { KEYCACHE_DBUG_PRINT("link_block: signal", ("thread %ld", thread->id)); keycache_pthread_cond_signal(&thread->suspend); unlink_from_queue(&keycache->waiting_for_block, thread); block->requests++; } } while (thread != last_thread); hash_link->block= block; /*
NOTE: We assigned the block to the hash_link and signalled the requesting thread(s). But it is possible that other threads runs first. These threads see the hash_link assigned to a block which is assigned to another hash_link and not marked BLOCK_IN_SWITCH. This can be a problem for functions that do not select the block via its hash_link: flush and free. They do only see a block which is in a "normal" state and don't know that it will be evicted soon.
We cannot set BLOCK_IN_SWITCH here because only one of the requesting threads must handle the eviction. All others must wait for it to complete. If we set the flag here, the threads would not know who is in charge of the eviction. Without the flag, the first thread takes the stick and sets the flag.
But we need to note in the block that is has been selected for eviction. It must not be freed. The evicting thread will not expect the block in the free list. Before freeing we could also check if block->requests > 1. But I think including another flag in the check of block->status is slightly more efficient and probably easier to read. */ block->status|= BLOCK_IN_EVICTION; KEYCACHE_THREAD_TRACE("link_block: after signaling");#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_PRINT("link_block", ("linked,unlinked block %u status=%x #requests=%u #available=%u", BLOCK_NUMBER(block), block->status, block->requests, keycache->blocks_available));#endif
return; }#else /* THREAD */
KEYCACHE_DBUG_ASSERT(! (!hot && keycache->waiting_for_block.last_thread)); /* Condition not transformed using DeMorgan, to keep the text identical */#endif /* THREAD */
pins= hot ? &keycache->used_ins : &keycache->used_last; ins= *pins; if (ins) { ins->next_used->prev_used= &block->next_used; block->next_used= ins->next_used; block->prev_used= &ins->next_used; ins->next_used= block; if (at_end) *pins= block; } else { /* The LRU ring is empty. Let the block point to itself. */ keycache->used_last= keycache->used_ins= block->next_used= block; block->prev_used= &block->next_used; } KEYCACHE_THREAD_TRACE("link_block");#if defined(KEYCACHE_DEBUG)
keycache->blocks_available++; KEYCACHE_DBUG_PRINT("link_block", ("linked block %u:%1u status=%x #requests=%u #available=%u", BLOCK_NUMBER(block), at_end, block->status, block->requests, keycache->blocks_available)); KEYCACHE_DBUG_ASSERT((ulong) keycache->blocks_available <= keycache->blocks_used);#endif
}
/*
Unlink a block from the LRU chain
SYNOPSIS unlink_block() keycache pointer to a key cache data structure block pointer to the block to unlink from the LRU chain
RETURN VALUE none
NOTES. See NOTES for link_block*/
static void unlink_block(KEY_CACHE *keycache, BLOCK_LINK *block){ DBUG_ASSERT((block->status & ~BLOCK_CHANGED) == (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ DBUG_ASSERT(!block->requests); DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); DBUG_ASSERT(block->next_used && block->prev_used && (block->next_used->prev_used == &block->next_used) && (*block->prev_used == block)); if (block->next_used == block) /* The list contains only one member */ keycache->used_last= keycache->used_ins= NULL; else { block->next_used->prev_used= block->prev_used; *block->prev_used= block->next_used; if (keycache->used_last == block) keycache->used_last= STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); if (keycache->used_ins == block) keycache->used_ins=STRUCT_PTR(BLOCK_LINK, next_used, block->prev_used); } block->next_used= NULL;#if !defined(DBUG_OFF)
/*
This makes it easier to see it's not in a chain during debugging. And some DBUG_ASSERT() rely on it. */ block->prev_used= NULL;#endif
KEYCACHE_THREAD_TRACE("unlink_block");#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_ASSERT(keycache->blocks_available != 0); keycache->blocks_available--; KEYCACHE_DBUG_PRINT("unlink_block", ("unlinked block %u status=%x #requests=%u #available=%u", BLOCK_NUMBER(block), block->status, block->requests, keycache->blocks_available));#endif
}
/*
Register requests for a block.
SYNOPSIS reg_requests() keycache Pointer to a key cache data structure. block Pointer to the block to register a request on. count Number of requests. Always 1.
NOTE The first request unlinks the block from the LRU ring. This means that it is protected against eveiction.
RETURN void*/static void reg_requests(KEY_CACHE *keycache, BLOCK_LINK *block, int count){ DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT(block->hash_link);
if (!block->requests) unlink_block(keycache, block); block->requests+=count;}
/*
Unregister request for a block linking it to the LRU chain if it's the last request
SYNOPSIS unreg_request() keycache pointer to a key cache data structure block pointer to the block to link to the LRU chain at_end <-> to link the block at the end of the LRU chain
RETURN VALUE none
NOTES. Every linking to the LRU ring decrements by one a special block counter (if it's positive). If the at_end parameter is TRUE the block is added either at the end of warm sub-chain or at the end of hot sub-chain. It is added to the hot subchain if its counter is zero and number of blocks in warm sub-chain is not less than some low limit (determined by the division_limit parameter). Otherwise the block is added to the warm sub-chain. If the at_end parameter is FALSE the block is always added at beginning of the warm sub-chain. Thus a warm block can be promoted to the hot sub-chain when its counter becomes zero for the first time. At the same time the block at the very beginning of the hot subchain might be moved to the beginning of the warm subchain if it stays untouched for a too long time (this time is determined by parameter age_threshold).
It is also possible that the block is selected for eviction and thus not linked in the LRU ring.*/
static void unreg_request(KEY_CACHE *keycache, BLOCK_LINK *block, int at_end){ DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(block->hash_link); /*backptr to block NULL from free_block()*/ DBUG_ASSERT(block->requests); DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); DBUG_ASSERT(!block->next_used); DBUG_ASSERT(!block->prev_used); /*
Unregister the request, but do not link erroneous blocks into the LRU ring. */ if (!--block->requests && !(block->status & BLOCK_ERROR)) { my_bool hot; if (block->hits_left) block->hits_left--; hot= !block->hits_left && at_end && keycache->warm_blocks > keycache->min_warm_blocks; if (hot) { if (block->temperature == BLOCK_WARM) keycache->warm_blocks--; block->temperature= BLOCK_HOT; KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu", keycache->warm_blocks)); } link_block(keycache, block, hot, (my_bool)at_end); block->last_hit_time= keycache->keycache_time; keycache->keycache_time++; /*
At this place, the block might be in the LRU ring or not. If an evicter was waiting for a block, it was selected for eviction and not linked in the LRU ring. */
/*
Check if we should link a hot block to the warm block sub-chain. It is possible that we select the same block as above. But it can also be another block. In any case a block from the LRU ring is selected. In other words it works even if the above block was selected for eviction and not linked in the LRU ring. Since this happens only if the LRU ring is empty, the block selected below would be NULL and the rest of the function skipped. */ block= keycache->used_ins; if (block && keycache->keycache_time - block->last_hit_time > keycache->age_threshold) { unlink_block(keycache, block); link_block(keycache, block, 0, 0); if (block->temperature != BLOCK_WARM) { keycache->warm_blocks++; block->temperature= BLOCK_WARM; } KEYCACHE_DBUG_PRINT("unreg_request", ("#warm_blocks: %lu", keycache->warm_blocks)); } }}
/*
Remove a reader of the page in block*/
static void remove_reader(BLOCK_LINK *block){ DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(block->hash_link && block->hash_link->block == block); DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); DBUG_ASSERT(!block->next_used); DBUG_ASSERT(!block->prev_used); DBUG_ASSERT(block->hash_link->requests);#ifdef THREAD
if (! --block->hash_link->requests && block->condvar) keycache_pthread_cond_signal(block->condvar);#else
--block->hash_link->requests;#endif
}
/*
Wait until the last reader of the page in block signals on its termination*/
static void wait_for_readers(KEY_CACHE *keycache, BLOCK_LINK *block){#ifdef THREAD
struct st_my_thread_var *thread= my_thread_var; DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(!(block->status & (BLOCK_IN_FLUSH | BLOCK_CHANGED))); DBUG_ASSERT(block->hash_link); DBUG_ASSERT(block->hash_link->block == block); /* Linked in file_blocks or changed_blocks hash. */ DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); /* Not linked in LRU ring. */ DBUG_ASSERT(!block->next_used); DBUG_ASSERT(!block->prev_used); while (block->hash_link->requests) { KEYCACHE_DBUG_PRINT("wait_for_readers: wait", ("suspend thread %ld block %u", thread->id, BLOCK_NUMBER(block))); /* There must be no other waiter. We have no queue here. */ DBUG_ASSERT(!block->condvar); block->condvar= &thread->suspend; keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock); block->condvar= NULL; }#else
KEYCACHE_DBUG_ASSERT(block->hash_link->requests == 0);#endif
}
/*
Add a hash link to a bucket in the hash_table*/
static inline void link_hash(HASH_LINK **start, HASH_LINK *hash_link){ if (*start) (*start)->prev= &hash_link->next; hash_link->next= *start; hash_link->prev= start; *start= hash_link;}
/*
Remove a hash link from the hash table*/
static void unlink_hash(KEY_CACHE *keycache, HASH_LINK *hash_link){ KEYCACHE_DBUG_PRINT("unlink_hash", ("fd: %u pos_ %lu #requests=%u", (uint) hash_link->file,(ulong) hash_link->diskpos, hash_link->requests)); KEYCACHE_DBUG_ASSERT(hash_link->requests == 0); if ((*hash_link->prev= hash_link->next)) hash_link->next->prev= hash_link->prev; hash_link->block= NULL;#ifdef THREAD
if (keycache->waiting_for_hash_link.last_thread) { /* Signal that a free hash link has appeared */ struct st_my_thread_var *last_thread= keycache->waiting_for_hash_link.last_thread; struct st_my_thread_var *first_thread= last_thread->next; struct st_my_thread_var *next_thread= first_thread; KEYCACHE_PAGE *first_page= (KEYCACHE_PAGE *) (first_thread->opt_info); struct st_my_thread_var *thread;
hash_link->file= first_page->file; hash_link->diskpos= first_page->filepos; do { KEYCACHE_PAGE *page; thread= next_thread; page= (KEYCACHE_PAGE *) thread->opt_info; next_thread= thread->next; /*
We notify about the event all threads that ask for the same page as the first thread in the queue */ if (page->file == hash_link->file && page->filepos == hash_link->diskpos) { KEYCACHE_DBUG_PRINT("unlink_hash: signal", ("thread %ld", thread->id)); keycache_pthread_cond_signal(&thread->suspend); unlink_from_queue(&keycache->waiting_for_hash_link, thread); } } while (thread != last_thread); link_hash(&keycache->hash_root[KEYCACHE_HASH(hash_link->file, hash_link->diskpos)], hash_link); return; }#else /* THREAD */
KEYCACHE_DBUG_ASSERT(! (keycache->waiting_for_hash_link.last_thread));#endif /* THREAD */
hash_link->next= keycache->free_hash_list; keycache->free_hash_list= hash_link;}
/*
Get the hash link for a page*/
static HASH_LINK *get_hash_link(KEY_CACHE *keycache, int file, my_off_t filepos){ reg1 HASH_LINK *hash_link, **start;#if defined(KEYCACHE_DEBUG)
int cnt;#endif
KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu", (uint) file,(ulong) filepos));
restart: /*
Find the bucket in the hash table for the pair (file, filepos); start contains the head of the bucket list, hash_link points to the first member of the list */ hash_link= *(start= &keycache->hash_root[KEYCACHE_HASH(file, filepos)]);#if defined(KEYCACHE_DEBUG)
cnt= 0;#endif
/* Look for an element for the pair (file, filepos) in the bucket chain */ while (hash_link && (hash_link->diskpos != filepos || hash_link->file != file)) { hash_link= hash_link->next;#if defined(KEYCACHE_DEBUG)
cnt++; if (! (cnt <= keycache->hash_links_used)) { int i; for (i=0, hash_link= *start ; i < cnt ; i++, hash_link= hash_link->next) { KEYCACHE_DBUG_PRINT("get_hash_link", ("fd: %u pos: %lu", (uint) hash_link->file,(ulong) hash_link->diskpos)); } } KEYCACHE_DBUG_ASSERT(cnt <= keycache->hash_links_used);#endif
} if (! hash_link) { /* There is no hash link in the hash table for the pair (file, filepos) */ if (keycache->free_hash_list) { hash_link= keycache->free_hash_list; keycache->free_hash_list= hash_link->next; } else if (keycache->hash_links_used < keycache->hash_links) { hash_link= &keycache->hash_link_root[keycache->hash_links_used++]; } else {#ifdef THREAD
/* Wait for a free hash link */ struct st_my_thread_var *thread= my_thread_var; KEYCACHE_PAGE page; KEYCACHE_DBUG_PRINT("get_hash_link", ("waiting")); page.file= file; page.filepos= filepos; thread->opt_info= (void *) &page; link_into_queue(&keycache->waiting_for_hash_link, thread); KEYCACHE_DBUG_PRINT("get_hash_link: wait", ("suspend thread %ld", thread->id)); keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock); thread->opt_info= NULL;#else
KEYCACHE_DBUG_ASSERT(0);#endif
goto restart; } hash_link->file= file; hash_link->diskpos= filepos; link_hash(start, hash_link); } /* Register the request for the page */ hash_link->requests++;
return hash_link;}
/*
Get a block for the file page requested by a keycache read/write operation; If the page is not in the cache return a free block, if there is none return the lru block after saving its buffer if the page is dirty.
SYNOPSIS
find_key_block() keycache pointer to a key cache data structure file handler for the file to read page from filepos position of the page in the file init_hits_left how initialize the block counter for the page wrmode <-> get for writing page_st out {PAGE_READ,PAGE_TO_BE_READ,PAGE_WAIT_TO_BE_READ}
RETURN VALUE Pointer to the found block if successful, 0 - otherwise
NOTES. For the page from file positioned at filepos the function checks whether the page is in the key cache specified by the first parameter. If this is the case it immediately returns the block. If not, the function first chooses a block for this page. If there is no not used blocks in the key cache yet, the function takes the block at the very beginning of the warm sub-chain. It saves the page in that block if it's dirty before returning the pointer to it. The function returns in the page_st parameter the following values: PAGE_READ - if page already in the block, PAGE_TO_BE_READ - if it is to be read yet by the current thread WAIT_TO_BE_READ - if it is to be read by another thread If an error occurs THE BLOCK_ERROR bit is set in the block status. It might happen that there are no blocks in LRU chain (in warm part) - all blocks are unlinked for some read/write operations. Then the function waits until first of this operations links any block back.*/
static BLOCK_LINK *find_key_block(KEY_CACHE *keycache, File file, my_off_t filepos, int init_hits_left, int wrmode, int *page_st){ HASH_LINK *hash_link; BLOCK_LINK *block; int error= 0; int page_status;
DBUG_ENTER("find_key_block"); KEYCACHE_THREAD_TRACE("find_key_block:begin"); DBUG_PRINT("enter", ("fd: %d pos: %lu wrmode: %d", file, (ulong) filepos, wrmode)); KEYCACHE_DBUG_PRINT("find_key_block", ("fd: %d pos: %lu wrmode: %d", file, (ulong) filepos, wrmode));#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache2", test_key_cache(keycache, "start of find_key_block", 0););#endif
restart: /*
If the flush phase of a resize operation fails, the cache is left unusable. This will be detected only after "goto restart". */ if (!keycache->can_be_used) DBUG_RETURN(0);
/*
Find the hash_link for the requested file block (file, filepos). We do always get a hash_link here. It has registered our request so that no other thread can use it for another file block until we release the request (which is done by remove_reader() usually). The hash_link can have a block assigned to it or not. If there is a block, it may be assigned to this hash_link or not. In cases where a block is evicted from the cache, it is taken from the LRU ring and referenced by the new hash_link. But the block can still be assigned to its old hash_link for some time if it needs to be flushed first, or if there are other threads still reading it.
Summary: hash_link is always returned. hash_link->block can be: - NULL or - not assigned to this hash_link or - assigned to this hash_link. If assigned, the block can have - invalid data (when freshly assigned) or - valid data. Valid data can be - changed over the file contents (dirty) or - not changed (clean). */ hash_link= get_hash_link(keycache, file, filepos); DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos));
page_status= -1; if ((block= hash_link->block) && block->hash_link == hash_link && (block->status & BLOCK_READ)) { /* Assigned block with valid (changed or unchanged) contents. */ page_status= PAGE_READ; } /*
else (page_status == -1) - block == NULL or - block not assigned to this hash_link or - block assigned but not yet read from file (invalid data). */
#ifdef THREAD
if (keycache->in_resize) { /* This is a request during a resize operation */
if (!block) { struct st_my_thread_var *thread;
/*
The file block is not in the cache. We don't need it in the cache: we are going to read or write directly to file. Cancel the request. We can simply decrement hash_link->requests because we did not release cache_lock since increasing it. So no other thread can wait for our request to become released. */ if (hash_link->requests == 1) { /*
We are the only one to request this hash_link (this file/pos). Free the hash_link. */ hash_link->requests--; unlink_hash(keycache, hash_link); DBUG_RETURN(0); }
/*
More requests on the hash_link. Someone tries to evict a block for this hash_link (could have started before resizing started). This means that the LRU ring is empty. Otherwise a block could be assigned immediately. Behave like a thread that wants to evict a block for this file/pos. Add to the queue of threads waiting for a block. Wait until there is one assigned.
Refresh the request on the hash-link so that it cannot be reused for another file/pos. */ thread= my_thread_var; thread->opt_info= (void *) hash_link; link_into_queue(&keycache->waiting_for_block, thread); do { KEYCACHE_DBUG_PRINT("find_key_block: wait", ("suspend thread %ld", thread->id)); keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock); } while (thread->next); thread->opt_info= NULL; /*
A block should now be assigned to the hash_link. But it may still need to be evicted. Anyway, we should re-check the situation. page_status must be set correctly. */ hash_link->requests--; goto restart; } /* end of if (!block) */
/*
There is a block for this file/pos in the cache. Register a request on it. This unlinks it from the LRU ring (if it is there) and hence protects it against eviction (if not already in eviction). We need this for returning the block to the caller, for calling remove_reader() (for debugging purposes), and for calling free_block(). The only case where we don't need the request is if the block is in eviction. In that case we have to unregister the request later. */ reg_requests(keycache, block, 1);
if (page_status != PAGE_READ) { /*
- block not assigned to this hash_link or - block assigned but not yet read from file (invalid data).
This must be a block in eviction. It will be read soon. We need to wait here until this happened. Otherwise the caller could access a wrong block or a block which is in read. While waiting we cannot lose hash_link nor block. We have registered a request on the hash_link. Everything can happen to the block but changes in the hash_link -> block relationship. In other words: everything can happen to the block but free or another completed eviction.
Note that we bahave like a secondary requestor here. We just cannot return with PAGE_WAIT_TO_BE_READ. This would work for read requests and writes on dirty blocks that are not in flush only. Waiting here on COND_FOR_REQUESTED works in all situations. */ DBUG_ASSERT(((block->hash_link != hash_link) && (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || ((block->hash_link == hash_link) && !(block->status & BLOCK_READ))); wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); /*
Here we can trust that the block has been assigned to this hash_link (block->hash_link == hash_link) and read into the buffer (BLOCK_READ). The worst things possible here are that the block is in free (BLOCK_REASSIGNED). But the block is still assigned to the hash_link. The freeing thread waits until we release our request on the hash_link. The block must not be again in eviction because we registered an request on it before starting to wait. */ DBUG_ASSERT(block->hash_link == hash_link); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))); } /*
The block is in the cache. Assigned to the hash_link. Valid data. Note that in case of page_st == PAGE_READ, the block can be marked for eviction. In any case it can be marked for freeing. */
if (!wrmode) { /* A reader can just read the block. */ *page_st= PAGE_READ; DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos) && (block->hash_link == hash_link)); DBUG_RETURN(block); }
/*
This is a writer. No two writers for the same block can exist. This must be assured by locks outside of the key cache. */ DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block));
while (block->status & BLOCK_IN_FLUSH) { /*
Wait until the block is flushed to file. Do not release the request on the hash_link yet to prevent that the block is freed or reassigned while we wait. While we wait, several things can happen to the block, including another flush. But the block cannot be reassigned to another hash_link until we release our request on it. But it can be marked BLOCK_REASSIGNED from free or eviction, while they wait for us to release the hash_link. */ wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); /*
If the flush phase failed, the resize could have finished while we waited here. */ if (!keycache->in_resize) { remove_reader(block); unreg_request(keycache, block, 1); goto restart; } DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(!(block->status & BLOCK_FOR_UPDATE) || fail_block(block)); DBUG_ASSERT(block->hash_link == hash_link); }
if (block->status & BLOCK_CHANGED) { /*
We want to write a block with changed contents. If the cache block size is bigger than the callers block size (e.g. MyISAM), the caller may replace part of the block only. Changes of the other part of the block must be preserved. Since the block has not yet been selected for flush, we can still add our changes. */ *page_st= PAGE_READ; DBUG_ASSERT((hash_link->file == file) && (hash_link->diskpos == filepos) && (block->hash_link == hash_link)); DBUG_RETURN(block); }
/*
This is a write request for a clean block. We do not want to have new dirty blocks in the cache while resizing. We will free the block and write directly to file. If the block is in eviction or in free, we just let it go.
Unregister from the hash_link. This must be done before freeing the block. And it must be done if not freeing the block. Because we could have waited above, we need to call remove_reader(). Other threads could wait for us to release our request on the hash_link. */ remove_reader(block);
/* If the block is not in eviction and not in free, we can free it. */ if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_REASSIGNED))) { /*
Free block as we are going to write directly to file. Although we have an exlusive lock for the updated key part, the control can be yielded by the current thread as we might have unfinished readers of other key parts in the block buffer. Still we are guaranteed not to have any readers of the key part we are writing into until the block is removed from the cache as we set the BLOCK_REASSIGNED flag (see the code below that handles reading requests). */ free_block(keycache, block); } else { /*
The block will be evicted/freed soon. Don't touch it in any way. Unregister the request that we registered above. */ unreg_request(keycache, block, 1);
/*
The block is still assigned to the hash_link (the file/pos that we are going to write to). Wait until the eviction/free is complete. Otherwise the direct write could complete before all readers are done with the block. So they could read outdated data.
Since we released our request on the hash_link, it can be reused for another file/pos. Hence we cannot just check for block->hash_link == hash_link. As long as the resize is proceeding the block cannot be reassigned to the same file/pos again. So we can terminate the loop when the block is no longer assigned to this file/pos. */ do { wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); /*
If the flush phase failed, the resize could have finished while we waited here. */ if (!keycache->in_resize) goto restart; } while (block->hash_link && (block->hash_link->file == file) && (block->hash_link->diskpos == filepos)); } DBUG_RETURN(0); }#else /* THREAD */
DBUG_ASSERT(!keycache->in_resize);#endif
if (page_status == PAGE_READ && (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_REASSIGNED))) { /*
This is a request for a block to be removed from cache. The block is assigned to this hash_link and contains valid data, but is marked for eviction or to be freed. Possible reasons why it has not yet been evicted/freed can be a flush before reassignment (BLOCK_IN_SWITCH), readers of the block have not finished yet (BLOCK_REASSIGNED), or the evicting thread did not yet awake after the block has been selected for it (BLOCK_IN_EVICTION). */
KEYCACHE_DBUG_PRINT("find_key_block", ("request for old page in block %u " "wrmode: %d block->status: %d", BLOCK_NUMBER(block), wrmode, block->status)); /*
Only reading requests can proceed until the old dirty page is flushed, all others are to be suspended, then resubmitted */ if (!wrmode && !(block->status & BLOCK_REASSIGNED)) { /*
This is a read request and the block not yet reassigned. We can register our request and proceed. This unlinks the block from the LRU ring and protects it against eviction. */ reg_requests(keycache, block, 1); } else { /*
Either this is a write request for a block that is in eviction or in free. We must not use it any more. Instead we must evict another block. But we cannot do this before the eviction/free is done. Otherwise we would find the same hash_link + block again and again.
Or this is a read request for a block in eviction/free that does not require a flush, but waits for readers to finish with the block. We do not read this block to let the eviction/free happen as soon as possible. Again we must wait so that we don't find the same hash_link + block again and again. */ DBUG_ASSERT(hash_link->requests); hash_link->requests--; KEYCACHE_DBUG_PRINT("find_key_block", ("request waiting for old page to be saved")); wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); KEYCACHE_DBUG_PRINT("find_key_block", ("request for old page resubmitted")); /*
The block is no longer assigned to this hash_link. Get another one. */ goto restart; } } else { /*
This is a request for a new block or for a block not to be removed. Either - block == NULL or - block not assigned to this hash_link or - block assigned but not yet read from file, or - block assigned with valid (changed or unchanged) data and - it will not be reassigned/freed. */ if (! block) { /* No block is assigned to the hash_link yet. */ if (keycache->blocks_unused) { if (keycache->free_block_list) { /* There is a block in the free list. */ block= keycache->free_block_list; keycache->free_block_list= block->next_used; block->next_used= NULL; } else { size_t block_mem_offset; /* There are some never used blocks, take first of them */ DBUG_ASSERT(keycache->blocks_used < (ulong) keycache->disk_blocks); block= &keycache->block_root[keycache->blocks_used]; block_mem_offset= ((size_t) keycache->blocks_used) * keycache->key_cache_block_size; block->buffer= ADD_TO_PTR(keycache->block_mem, block_mem_offset, uchar*); keycache->blocks_used++; DBUG_ASSERT(!block->next_used); } DBUG_ASSERT(!block->prev_used); DBUG_ASSERT(!block->next_changed); DBUG_ASSERT(!block->prev_changed); DBUG_ASSERT(!block->hash_link); DBUG_ASSERT(!block->status); DBUG_ASSERT(!block->requests); keycache->blocks_unused--; block->status= BLOCK_IN_USE; block->length= 0; block->offset= keycache->key_cache_block_size; block->requests= 1; block->temperature= BLOCK_COLD; block->hits_left= init_hits_left; block->last_hit_time= 0; block->hash_link= hash_link; hash_link->block= block; link_to_file_list(keycache, block, file, 0); page_status= PAGE_TO_BE_READ; KEYCACHE_DBUG_PRINT("find_key_block", ("got free or never used block %u", BLOCK_NUMBER(block))); } else { /*
There are no free blocks and no never used blocks, use a block from the LRU ring. */
#ifdef THREAD
if (! keycache->used_last) { /*
The LRU ring is empty. Wait until a new block is added to it. Several threads might wait here for the same hash_link, all of them must get the same block. While waiting for a block, after a block is selected for this hash_link, other threads can run first before this one awakes. During this time interval other threads find this hash_link pointing to the block, which is still assigned to another hash_link. In this case the block is not marked BLOCK_IN_SWITCH yet, but it is marked BLOCK_IN_EVICTION. */
struct st_my_thread_var *thread= my_thread_var; thread->opt_info= (void *) hash_link; link_into_queue(&keycache->waiting_for_block, thread); do { KEYCACHE_DBUG_PRINT("find_key_block: wait", ("suspend thread %ld", thread->id)); keycache_pthread_cond_wait(&thread->suspend, &keycache->cache_lock); } while (thread->next); thread->opt_info= NULL; /* Assert that block has a request registered. */ DBUG_ASSERT(hash_link->block->requests); /* Assert that block is not in LRU ring. */ DBUG_ASSERT(!hash_link->block->next_used); DBUG_ASSERT(!hash_link->block->prev_used); }#else
KEYCACHE_DBUG_ASSERT(keycache->used_last);#endif
/*
If we waited above, hash_link->block has been assigned by link_block(). Otherwise it is still NULL. In the latter case we need to grab a block from the LRU ring ourselves. */ block= hash_link->block; if (! block) { /* Select the last block from the LRU ring. */ block= keycache->used_last->next_used; block->hits_left= init_hits_left; block->last_hit_time= 0; hash_link->block= block; /*
Register a request on the block. This unlinks it from the LRU ring and protects it against eviction. */ DBUG_ASSERT(!block->requests); reg_requests(keycache, block,1); /*
We do not need to set block->status|= BLOCK_IN_EVICTION here because we will set block->status|= BLOCK_IN_SWITCH immediately without releasing the lock in between. This does also support debugging. When looking at the block, one can see if the block has been selected by link_block() after the LRU ring was empty, or if it was grabbed directly from the LRU ring in this branch. */ }
/*
If we had to wait above, there is a small chance that another thread grabbed this block for the same file block already. But in most cases the first condition is true. */ if (block->hash_link != hash_link && ! (block->status & BLOCK_IN_SWITCH) ) { /* this is a primary request for a new page */ block->status|= BLOCK_IN_SWITCH;
KEYCACHE_DBUG_PRINT("find_key_block", ("got block %u for new page", BLOCK_NUMBER(block)));
if (block->status & BLOCK_CHANGED) { /* The block contains a dirty page - push it out of the cache */
KEYCACHE_DBUG_PRINT("find_key_block", ("block is dirty")); if (block->status & BLOCK_IN_FLUSH) { /*
The block is marked for flush. If we do not wait here, it could happen that we write the block, reassign it to another file block, then, before the new owner can read the new file block, the flusher writes the cache block (which still has the old contents) to the new file block! */ wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); /*
The block is marked BLOCK_IN_SWITCH. It should be left alone except for reading. No free, no write. */ DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); DBUG_ASSERT(!(block->status & (BLOCK_REASSIGNED | BLOCK_CHANGED | BLOCK_FOR_UPDATE))); } else { block->status|= BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE; /*
BLOCK_IN_EVICTION may be true or not. Other flags must have a fixed value. */ DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == (BLOCK_READ | BLOCK_IN_SWITCH | BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | BLOCK_CHANGED | BLOCK_IN_USE)); DBUG_ASSERT(block->hash_link);
keycache_pthread_mutex_unlock(&keycache->cache_lock); /*
The call is thread safe because only the current thread might change the block->hash_link value */ error= my_pwrite(block->hash_link->file, block->buffer + block->offset, block->length - block->offset, block->hash_link->diskpos + block->offset, MYF(MY_NABP | MY_WAIT_IF_FULL)); keycache_pthread_mutex_lock(&keycache->cache_lock);
/* Block status must not have changed. */ DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == (BLOCK_READ | BLOCK_IN_SWITCH | BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE | BLOCK_CHANGED | BLOCK_IN_USE) || fail_block(block)); keycache->global_cache_write++; } }
block->status|= BLOCK_REASSIGNED; /*
The block comes from the LRU ring. It must have a hash_link assigned. */ DBUG_ASSERT(block->hash_link); if (block->hash_link) { /*
All pending requests for this page must be resubmitted. This must be done before waiting for readers. They could wait for the flush to complete. And we must also do it after the wait. Flushers might try to free the block while we wait. They would wait until the reassignment is complete. Also the block status must reflect the correct situation: The block is not changed nor in flush any more. Note that we must not change the BLOCK_CHANGED flag outside of link_to_file_list() so that it is always in the correct queue and the *blocks_changed counters are correct. */ block->status&= ~(BLOCK_IN_FLUSH | BLOCK_IN_FLUSHWRITE); link_to_file_list(keycache, block, block->hash_link->file, 1); release_whole_queue(&block->wqueue[COND_FOR_SAVED]); /*
The block is still assigned to its old hash_link. Wait until all pending read requests for this page are executed (we could have avoided this waiting, if we had read a page in the cache in a sweep, without yielding control) */ wait_for_readers(keycache, block); DBUG_ASSERT(block->hash_link && block->hash_link->block == block && block->prev_changed); /* The reader must not have been a writer. */ DBUG_ASSERT(!(block->status & BLOCK_CHANGED));
/* Wake flushers that might have found the block in between. */ release_whole_queue(&block->wqueue[COND_FOR_SAVED]);
/* Remove the hash link for the old file block from the hash. */ unlink_hash(keycache, block->hash_link);
/*
For sanity checks link_to_file_list() asserts that block and hash_link refer to each other. Hence we need to assign the hash_link first, but then we would not know if it was linked before. Hence we would not know if to unlink it. So unlink it here and call link_to_file_list(..., FALSE). */ unlink_changed(block); } block->status= error ? BLOCK_ERROR : BLOCK_IN_USE ; block->length= 0; block->offset= keycache->key_cache_block_size; block->hash_link= hash_link; link_to_file_list(keycache, block, file, 0); page_status= PAGE_TO_BE_READ;
KEYCACHE_DBUG_ASSERT(block->hash_link->block == block); KEYCACHE_DBUG_ASSERT(hash_link->block->hash_link == hash_link); } else { /*
Either (block->hash_link == hash_link), or (block->status & BLOCK_IN_SWITCH).
This is for secondary requests for a new file block only. Either it is already assigned to the new hash_link meanwhile (if we had to wait due to empty LRU), or it is already in eviction by another thread. Since this block has been grabbed from the LRU ring and attached to this hash_link, another thread cannot grab the same block from the LRU ring anymore. If the block is in eviction already, it must become attached to the same hash_link and as such destined for the same file block. */ KEYCACHE_DBUG_PRINT("find_key_block", ("block->hash_link: %p hash_link: %p " "block->status: %u", block->hash_link, hash_link, block->status )); page_status= (((block->hash_link == hash_link) && (block->status & BLOCK_READ)) ? PAGE_READ : PAGE_WAIT_TO_BE_READ); } } } else { /*
Block is not NULL. This hash_link points to a block. Either - block not assigned to this hash_link (yet) or - block assigned but not yet read from file, or - block assigned with valid (changed or unchanged) data and - it will not be reassigned/freed.
The first condition means hash_link points to a block in eviction. This is not necessarily marked by BLOCK_IN_SWITCH yet. But then it is marked BLOCK_IN_EVICTION. See the NOTE in link_block(). In both cases it is destined for this hash_link and its file block address. When this hash_link got its block address, the block was removed from the LRU ring and cannot be selected for eviction (for another hash_link) again.
Register a request on the block. This is another protection against eviction. */ DBUG_ASSERT(((block->hash_link != hash_link) && (block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) || ((block->hash_link == hash_link) && !(block->status & BLOCK_READ)) || ((block->status & BLOCK_READ) && !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH)))); reg_requests(keycache, block, 1); KEYCACHE_DBUG_PRINT("find_key_block", ("block->hash_link: %p hash_link: %p " "block->status: %u", block->hash_link, hash_link, block->status )); page_status= (((block->hash_link == hash_link) && (block->status & BLOCK_READ)) ? PAGE_READ : PAGE_WAIT_TO_BE_READ); } }
KEYCACHE_DBUG_ASSERT(page_status != -1); /* Same assert basically, but be very sure. */ KEYCACHE_DBUG_ASSERT(block); /* Assert that block has a request and is not in LRU ring. */ DBUG_ASSERT(block->requests); DBUG_ASSERT(!block->next_used); DBUG_ASSERT(!block->prev_used); /* Assert that we return the correct block. */ DBUG_ASSERT((page_status == PAGE_WAIT_TO_BE_READ) || ((block->hash_link->file == file) && (block->hash_link->diskpos == filepos))); *page_st=page_status; KEYCACHE_DBUG_PRINT("find_key_block", ("fd: %d pos: %lu block->status: %u page_status: %d", file, (ulong) filepos, block->status, page_status));
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache2", test_key_cache(keycache, "end of find_key_block",0););#endif
KEYCACHE_THREAD_TRACE("find_key_block:end"); DBUG_RETURN(block);}
/*
Read into a key cache block buffer from disk.
SYNOPSIS
read_block() keycache pointer to a key cache data structure block block to which buffer the data is to be read read_length size of data to be read min_length at least so much data must be read primary <-> the current thread will read the data
RETURN VALUE None
NOTES. The function either reads a page data from file to the block buffer, or waits until another thread reads it. What page to read is determined by a block parameter - reference to a hash link for this page. If an error occurs THE BLOCK_ERROR bit is set in the block status. We do not report error when the size of successfully read portion is less than read_length, but not less than min_length.*/
static void read_block(KEY_CACHE *keycache, BLOCK_LINK *block, uint read_length, uint min_length, my_bool primary){ size_t got_length;
/* On entry cache_lock is locked */
KEYCACHE_THREAD_TRACE("read_block"); if (primary) { /*
This code is executed only by threads that submitted primary requests. Until block->status contains BLOCK_READ, all other request for the block become secondary requests. For a primary request the block must be properly initialized. */ DBUG_ASSERT(((block->status & ~BLOCK_FOR_UPDATE) == BLOCK_IN_USE) || fail_block(block)); DBUG_ASSERT((block->length == 0) || fail_block(block)); DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || fail_block(block)); DBUG_ASSERT((block->requests > 0) || fail_block(block));
KEYCACHE_DBUG_PRINT("read_block", ("page to be read by primary request"));
keycache->global_cache_read++; /* Page is not in buffer yet, is to be read from disk */ keycache_pthread_mutex_unlock(&keycache->cache_lock); /*
Here other threads may step in and register as secondary readers. They will register in block->wqueue[COND_FOR_REQUESTED]. */ got_length= my_pread(block->hash_link->file, block->buffer, read_length, block->hash_link->diskpos, MYF(0)); keycache_pthread_mutex_lock(&keycache->cache_lock); /*
The block can now have been marked for free (in case of FLUSH_RELEASE). Otherwise the state must be unchanged. */ DBUG_ASSERT(((block->status & ~(BLOCK_REASSIGNED | BLOCK_FOR_UPDATE)) == BLOCK_IN_USE) || fail_block(block)); DBUG_ASSERT((block->length == 0) || fail_block(block)); DBUG_ASSERT((block->offset == keycache->key_cache_block_size) || fail_block(block)); DBUG_ASSERT((block->requests > 0) || fail_block(block));
if (got_length < min_length) block->status|= BLOCK_ERROR; else { block->status|= BLOCK_READ; block->length= got_length; /*
Do not set block->offset here. If this block is marked BLOCK_CHANGED later, we want to flush only the modified part. So only a writer may set block->offset down from keycache->key_cache_block_size. */ } KEYCACHE_DBUG_PRINT("read_block", ("primary request: new page in cache")); /* Signal that all pending requests for this page now can be processed */ release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); } else { /*
This code is executed only by threads that submitted secondary requests. At this point it could happen that the cache block is not yet assigned to the hash_link for the requested file block. But at awake from the wait this should be the case. Unfortunately we cannot assert this here because we do not know the hash_link for the requested file block nor the file and position. So we have to assert this in the caller. */ KEYCACHE_DBUG_PRINT("read_block", ("secondary request waiting for new page to be read")); wait_on_queue(&block->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); KEYCACHE_DBUG_PRINT("read_block", ("secondary request: new page in cache")); }}
/*
Read a block of data from a cached file into a buffer;
SYNOPSIS
key_cache_read() keycache pointer to a key cache data structure file handler for the file for the block of data to be read filepos position of the block of data in the file level determines the weight of the data buff buffer to where the data must be placed length length of the buffer block_length length of the block in the key cache buffer return_buffer return pointer to the key cache buffer with the data
RETURN VALUE Returns address from where the data is placed if sucessful, 0 - otherwise.
NOTES. The function ensures that a block of data of size length from file positioned at filepos is in the buffers for some key cache blocks. Then the function either copies the data into the buffer buff, or, if return_buffer is TRUE, it just returns the pointer to the key cache buffer with the data. Filepos must be a multiple of 'block_length', but it doesn't have to be a multiple of key_cache_block_size;*/
uchar *key_cache_read(KEY_CACHE *keycache, File file, my_off_t filepos, int level, uchar *buff, uint length, uint block_length __attribute__((unused)), int return_buffer __attribute__((unused))){ my_bool locked_and_incremented= FALSE; int error=0; uchar *start= buff; DBUG_ENTER("key_cache_read"); DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", (uint) file, (ulong) filepos, length));
if (keycache->key_cache_inited) { /* Key cache is used */ reg1 BLOCK_LINK *block; uint read_length; uint offset; int page_st;
if (MYSQL_KEYCACHE_READ_START_ENABLED()) { MYSQL_KEYCACHE_READ_START(my_filename(file), length, (ulong) (keycache->blocks_used * keycache->key_cache_block_size), (ulong) (keycache->blocks_unused * keycache->key_cache_block_size)); } /*
When the key cache is once initialized, we use the cache_lock to reliably distinguish the cases of normal operation, resizing, and disabled cache. We always increment and decrement 'cnt_for_resize_op' so that a resizer can wait for pending I/O. */ keycache_pthread_mutex_lock(&keycache->cache_lock); /*
Cache resizing has two phases: Flushing and re-initializing. In the flush phase read requests are allowed to bypass the cache for blocks not in the cache. find_key_block() returns NULL in this case.
After the flush phase new I/O requests must wait until the re-initialization is done. The re-initialization can be done only if no I/O request is in progress. The reason is that key_cache_block_size can change. With enabled cache, I/O is done in chunks of key_cache_block_size. Every chunk tries to use a cache block first. If the block size changes in the middle, a block could be missed and old data could be read. */ while (keycache->in_resize && !keycache->resize_in_flush) wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); /* Register the I/O for the next resize. */ inc_counter_for_resize_op(keycache); locked_and_incremented= TRUE; /* Requested data may not always be aligned to cache blocks. */ offset= (uint) (filepos % keycache->key_cache_block_size); /* Read data in key_cache_block_size increments */ do { /* Cache could be disabled in a later iteration. */ if (!keycache->can_be_used) { KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache cannot be used")); goto no_key_cache; } /* Start reading at the beginning of the cache block. */ filepos-= offset; /* Do not read beyond the end of the cache block. */ read_length= length; set_if_smaller(read_length, keycache->key_cache_block_size-offset); KEYCACHE_DBUG_ASSERT(read_length > 0);
#ifndef THREAD
if (block_length > keycache->key_cache_block_size || offset) return_buffer=0;#endif
/* Request the cache block that matches file/pos. */ keycache->global_cache_r_requests++;
MYSQL_KEYCACHE_READ_BLOCK(keycache->key_cache_block_size);
block=find_key_block(keycache, file, filepos, level, 0, &page_st); if (!block) { /*
This happens only for requests submitted during key cache resize. The block is not in the cache and shall not go in. Read directly from file. */ keycache->global_cache_read++; keycache_pthread_mutex_unlock(&keycache->cache_lock); error= (my_pread(file, (uchar*) buff, read_length, filepos + offset, MYF(MY_NABP)) != 0); keycache_pthread_mutex_lock(&keycache->cache_lock); goto next_block; } if (!(block->status & BLOCK_ERROR)) { if (page_st != PAGE_READ) { MYSQL_KEYCACHE_READ_MISS(); /* The requested page is to be read into the block buffer */ read_block(keycache, block, keycache->key_cache_block_size, read_length+offset, (my_bool)(page_st == PAGE_TO_BE_READ)); /*
A secondary request must now have the block assigned to the requested file block. It does not hurt to check it for primary requests too. */ DBUG_ASSERT(keycache->can_be_used); DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT(block->hash_link->diskpos == filepos); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); } else if (block->length < read_length + offset) { /*
Impossible if nothing goes wrong: this could only happen if we are using a file with small key blocks and are trying to read outside the file */ my_errno= -1; block->status|= BLOCK_ERROR; } else { MYSQL_KEYCACHE_READ_HIT(); } }
/* block status may have added BLOCK_ERROR in the above 'if'. */ if (!(block->status & BLOCK_ERROR)) {#ifndef THREAD
if (! return_buffer)#endif
{ DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock);#endif
/* Copy data from the cache buffer */ if (!(read_length & 511)) bmove512(buff, block->buffer+offset, read_length); else memcpy(buff, block->buffer+offset, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE));#endif
} }
remove_reader(block);
/* Error injection for coverage testing. */ DBUG_EXECUTE_IF("key_cache_read_block_error", block->status|= BLOCK_ERROR;);
/* Do not link erroneous blocks into the LRU ring, but free them. */ if (!(block->status & BLOCK_ERROR)) { /*
Link the block into the LRU ring if it's the last submitted request for the block. This enables eviction for the block. */ unreg_request(keycache, block, 1); } else { free_block(keycache, block); error= 1; break; }
#ifndef THREAD
/* This is only true if we where able to read everything in one block */ if (return_buffer) { if (MYSQL_KEYCACHE_READ_DONE_ENABLED()) { MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used * keycache->key_cache_block_size), (ulong) (keycache->blocks_unused * keycache->key_cache_block_size)); } DBUG_RETURN(block->buffer); }#endif
next_block: buff+= read_length; filepos+= read_length+offset; offset= 0;
} while ((length-= read_length)); if (MYSQL_KEYCACHE_READ_DONE_ENABLED()) { MYSQL_KEYCACHE_READ_DONE((ulong) (keycache->blocks_used * keycache->key_cache_block_size), (ulong) (keycache->blocks_unused * keycache->key_cache_block_size)); } goto end; } KEYCACHE_DBUG_PRINT("key_cache_read", ("keycache not initialized"));
no_key_cache: /* Key cache is not used */
keycache->global_cache_r_requests++; keycache->global_cache_read++;
if (locked_and_incremented) keycache_pthread_mutex_unlock(&keycache->cache_lock); if (my_pread(file, (uchar*) buff, length, filepos, MYF(MY_NABP))) error= 1; if (locked_and_incremented) keycache_pthread_mutex_lock(&keycache->cache_lock);
end: if (locked_and_incremented) { dec_counter_for_resize_op(keycache); keycache_pthread_mutex_unlock(&keycache->cache_lock); } DBUG_PRINT("exit", ("error: %d", error )); DBUG_RETURN(error ? (uchar*) 0 : start);}
/*
Insert a block of file data from a buffer into key cache
SYNOPSIS key_cache_insert() keycache pointer to a key cache data structure file handler for the file to insert data from filepos position of the block of data in the file to insert level determines the weight of the data buff buffer to read data from length length of the data in the buffer
NOTES This is used by MyISAM to move all blocks from a index file to the key cache
RETURN VALUE 0 if a success, 1 - otherwise.*/
int key_cache_insert(KEY_CACHE *keycache, File file, my_off_t filepos, int level, uchar *buff, uint length){ int error= 0; DBUG_ENTER("key_cache_insert"); DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u", (uint) file,(ulong) filepos, length));
if (keycache->key_cache_inited) { /* Key cache is used */ reg1 BLOCK_LINK *block; uint read_length; uint offset; int page_st; my_bool locked_and_incremented= FALSE;
/*
When the keycache is once initialized, we use the cache_lock to reliably distinguish the cases of normal operation, resizing, and disabled cache. We always increment and decrement 'cnt_for_resize_op' so that a resizer can wait for pending I/O. */ keycache_pthread_mutex_lock(&keycache->cache_lock); /*
We do not load index data into a disabled cache nor into an ongoing resize. */ if (!keycache->can_be_used || keycache->in_resize) goto no_key_cache; /* Register the pseudo I/O for the next resize. */ inc_counter_for_resize_op(keycache); locked_and_incremented= TRUE; /* Loaded data may not always be aligned to cache blocks. */ offset= (uint) (filepos % keycache->key_cache_block_size); /* Load data in key_cache_block_size increments. */ do { /* Cache could be disabled or resizing in a later iteration. */ if (!keycache->can_be_used || keycache->in_resize) goto no_key_cache; /* Start loading at the beginning of the cache block. */ filepos-= offset; /* Do not load beyond the end of the cache block. */ read_length= length; set_if_smaller(read_length, keycache->key_cache_block_size-offset); KEYCACHE_DBUG_ASSERT(read_length > 0);
/* The block has been read by the caller already. */ keycache->global_cache_read++; /* Request the cache block that matches file/pos. */ keycache->global_cache_r_requests++; block= find_key_block(keycache, file, filepos, level, 0, &page_st); if (!block) { /*
This happens only for requests submitted during key cache resize. The block is not in the cache and shall not go in. Stop loading index data. */ goto no_key_cache; } if (!(block->status & BLOCK_ERROR)) { if ((page_st == PAGE_WAIT_TO_BE_READ) || ((page_st == PAGE_TO_BE_READ) && (offset || (read_length < keycache->key_cache_block_size)))) { /*
Either
this is a secondary request for a block to be read into the cache. The block is in eviction. It is not yet assigned to the requested file block (It does not point to the right hash_link). So we cannot call remove_reader() on the block. And we cannot access the hash_link directly here. We need to wait until the assignment is complete. read_block() executes the correct wait when called with primary == FALSE.
Or
this is a primary request for a block to be read into the cache and the supplied data does not fill the whole block.
This function is called on behalf of a LOAD INDEX INTO CACHE statement, which is a read-only task and allows other readers. It is possible that a parallel running reader tries to access this block. If it needs more data than has been supplied here, it would report an error. To be sure that we have all data in the block that is available in the file, we read the block ourselves.
Though reading again what the caller did read already is an expensive operation, we need to do this for correctness. */ read_block(keycache, block, keycache->key_cache_block_size, read_length + offset, (page_st == PAGE_TO_BE_READ)); /*
A secondary request must now have the block assigned to the requested file block. It does not hurt to check it for primary requests too. */ DBUG_ASSERT(keycache->can_be_used); DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT(block->hash_link->diskpos == filepos); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); } else if (page_st == PAGE_TO_BE_READ) { /*
This is a new block in the cache. If we come here, we have data for the whole block. */ DBUG_ASSERT(block->hash_link->requests); DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ));
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock); /*
Here other threads may step in and register as secondary readers. They will register in block->wqueue[COND_FOR_REQUESTED]. */#endif
/* Copy data from buff */ if (!(read_length & 511)) bmove512(block->buffer+offset, buff, read_length); else memcpy(block->buffer+offset, buff, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock); DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ));#endif
/*
After the data is in the buffer, we can declare the block valid. Now other threads do not need to register as secondary readers any more. They can immediately access the block. */ block->status|= BLOCK_READ; block->length= read_length+offset; /*
Do not set block->offset here. If this block is marked BLOCK_CHANGED later, we want to flush only the modified part. So only a writer may set block->offset down from keycache->key_cache_block_size. */ KEYCACHE_DBUG_PRINT("key_cache_insert", ("primary request: new page in cache")); /* Signal all pending requests. */ release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]); } else { /*
page_st == PAGE_READ. The block is in the buffer. All data must already be present. Blocks are always read with all data available on file. Assert that the block does not have less contents than the preloader supplies. If the caller has data beyond block->length, it means that a file write has been done while this block was in cache and not extended with the new data. If the condition is met, we can simply ignore the block. */ DBUG_ASSERT((page_st == PAGE_READ) && (read_length + offset <= block->length)); }
/*
A secondary request must now have the block assigned to the requested file block. It does not hurt to check it for primary requests too. */ DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT(block->hash_link->diskpos == filepos); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); } /* end of if (!(block->status & BLOCK_ERROR)) */
remove_reader(block);
/* Error injection for coverage testing. */ DBUG_EXECUTE_IF("key_cache_insert_block_error", block->status|= BLOCK_ERROR; errno=EIO;);
/* Do not link erroneous blocks into the LRU ring, but free them. */ if (!(block->status & BLOCK_ERROR)) { /*
Link the block into the LRU ring if it's the last submitted request for the block. This enables eviction for the block. */ unreg_request(keycache, block, 1); } else { free_block(keycache, block); error= 1; break; }
buff+= read_length; filepos+= read_length+offset; offset= 0;
} while ((length-= read_length));
no_key_cache: if (locked_and_incremented) dec_counter_for_resize_op(keycache); keycache_pthread_mutex_unlock(&keycache->cache_lock); } DBUG_RETURN(error);}
/*
Write a buffer into a cached file.
SYNOPSIS
key_cache_write() keycache pointer to a key cache data structure file handler for the file to write data to filepos position in the file to write data to level determines the weight of the data buff buffer with the data length length of the buffer dont_write if is 0 then all dirty pages involved in writing should have been flushed from key cache
RETURN VALUE 0 if a success, 1 - otherwise.
NOTES. The function copies the data of size length from buff into buffers for key cache blocks that are assigned to contain the portion of the file starting with position filepos. It ensures that this data is flushed to the file if dont_write is FALSE. Filepos must be a multiple of 'block_length', but it doesn't have to be a multiple of key_cache_block_size;
dont_write is always TRUE in the server (info->lock_type is never F_UNLCK).*/
int key_cache_write(KEY_CACHE *keycache, File file, my_off_t filepos, int level, uchar *buff, uint length, uint block_length __attribute__((unused)), int dont_write){ my_bool locked_and_incremented= FALSE; int error=0; DBUG_ENTER("key_cache_write"); DBUG_PRINT("enter", ("fd: %u pos: %lu length: %u block_length: %u" " key_block_length: %u", (uint) file, (ulong) filepos, length, block_length, keycache ? keycache->key_cache_block_size : 0));
if (!dont_write) { /* purecov: begin inspected */ /* Not used in the server. */ /* Force writing from buff into disk. */ keycache->global_cache_w_requests++; keycache->global_cache_write++; if (my_pwrite(file, buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL))) DBUG_RETURN(1); /* purecov: end */ }
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache", test_key_cache(keycache, "start of key_cache_write", 1););#endif
if (keycache->key_cache_inited) { /* Key cache is used */ reg1 BLOCK_LINK *block; uint read_length; uint offset; int page_st;
if (MYSQL_KEYCACHE_WRITE_START_ENABLED()) { MYSQL_KEYCACHE_WRITE_START(my_filename(file), length, (ulong) (keycache->blocks_used * keycache->key_cache_block_size), (ulong) (keycache->blocks_unused * keycache->key_cache_block_size)); }
/*
When the key cache is once initialized, we use the cache_lock to reliably distinguish the cases of normal operation, resizing, and disabled cache. We always increment and decrement 'cnt_for_resize_op' so that a resizer can wait for pending I/O. */ keycache_pthread_mutex_lock(&keycache->cache_lock); /*
Cache resizing has two phases: Flushing and re-initializing. In the flush phase write requests can modify dirty blocks that are not yet in flush. Otherwise they are allowed to bypass the cache. find_key_block() returns NULL in both cases (clean blocks and non-cached blocks).
After the flush phase new I/O requests must wait until the re-initialization is done. The re-initialization can be done only if no I/O request is in progress. The reason is that key_cache_block_size can change. With enabled cache I/O is done in chunks of key_cache_block_size. Every chunk tries to use a cache block first. If the block size changes in the middle, a block could be missed and data could be written below a cached block. */ while (keycache->in_resize && !keycache->resize_in_flush) wait_on_queue(&keycache->resize_queue, &keycache->cache_lock); /* Register the I/O for the next resize. */ inc_counter_for_resize_op(keycache); locked_and_incremented= TRUE; /* Requested data may not always be aligned to cache blocks. */ offset= (uint) (filepos % keycache->key_cache_block_size); /* Write data in key_cache_block_size increments. */ do { /* Cache could be disabled in a later iteration. */ if (!keycache->can_be_used) goto no_key_cache;
MYSQL_KEYCACHE_WRITE_BLOCK(keycache->key_cache_block_size); /* Start writing at the beginning of the cache block. */ filepos-= offset; /* Do not write beyond the end of the cache block. */ read_length= length; set_if_smaller(read_length, keycache->key_cache_block_size-offset); KEYCACHE_DBUG_ASSERT(read_length > 0);
/* Request the cache block that matches file/pos. */ keycache->global_cache_w_requests++; block= find_key_block(keycache, file, filepos, level, 1, &page_st); if (!block) { /*
This happens only for requests submitted during key cache resize. The block is not in the cache and shall not go in. Write directly to file. */ if (dont_write) { /* Used in the server. */ keycache->global_cache_write++; keycache_pthread_mutex_unlock(&keycache->cache_lock); if (my_pwrite(file, (uchar*) buff, read_length, filepos + offset, MYF(MY_NABP | MY_WAIT_IF_FULL))) error=1; keycache_pthread_mutex_lock(&keycache->cache_lock); } goto next_block; } /*
Prevent block from flushing and from being selected for to be freed. This must be set when we release the cache_lock. However, we must not set the status of the block before it is assigned to this file/pos. */ if (page_st != PAGE_WAIT_TO_BE_READ) block->status|= BLOCK_FOR_UPDATE; /*
We must read the file block first if it is not yet in the cache and we do not replace all of its contents.
In cases where the cache block is big enough to contain (parts of) index blocks of different indexes, our request can be secondary (PAGE_WAIT_TO_BE_READ). In this case another thread is reading the file block. If the read completes after us, it overwrites our new contents with the old contents. So we have to wait for the other thread to complete the read of this block. read_block() takes care for the wait. */ if (!(block->status & BLOCK_ERROR) && ((page_st == PAGE_TO_BE_READ && (offset || read_length < keycache->key_cache_block_size)) || (page_st == PAGE_WAIT_TO_BE_READ))) { read_block(keycache, block, offset + read_length >= keycache->key_cache_block_size? offset : keycache->key_cache_block_size, offset, (page_st == PAGE_TO_BE_READ)); DBUG_ASSERT(keycache->can_be_used); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); /*
Prevent block from flushing and from being selected for to be freed. This must be set when we release the cache_lock. Here we set it in case we could not set it above. */ block->status|= BLOCK_FOR_UPDATE; } /*
The block should always be assigned to the requested file block here. It need not be BLOCK_READ when overwriting the whole block. */ DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT(block->hash_link->diskpos == filepos); DBUG_ASSERT(block->status & BLOCK_IN_USE); DBUG_ASSERT((page_st == PAGE_TO_BE_READ) || (block->status & BLOCK_READ)); /*
The block to be written must not be marked BLOCK_REASSIGNED. Otherwise it could be freed in dirty state or reused without another flush during eviction. It must also not be in flush. Otherwise the old contens may have been flushed already and the flusher could clear BLOCK_CHANGED without flushing the new changes again. */ DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED));
while (block->status & BLOCK_IN_FLUSHWRITE) { /*
Another thread is flushing the block. It was dirty already. Wait until the block is flushed to file. Otherwise we could modify the buffer contents just while it is written to file. An unpredictable file block contents would be the result. While we wait, several things can happen to the block, including another flush. But the block cannot be reassigned to another hash_link until we release our request on it. */ wait_on_queue(&block->wqueue[COND_FOR_SAVED], &keycache->cache_lock); DBUG_ASSERT(keycache->can_be_used); DBUG_ASSERT(block->status & (BLOCK_READ | BLOCK_IN_USE)); /* Still must not be marked for free. */ DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); DBUG_ASSERT(block->hash_link && (block->hash_link->block == block)); }
/*
We could perhaps release the cache_lock during access of the data like in the other functions. Locks outside of the key cache assure that readers and a writer do not access the same range of data. Parallel accesses should happen only if the cache block contains multiple index block(fragment)s. So different parts of the buffer would be read/written. An attempt to flush during memcpy() is prevented with BLOCK_FOR_UPDATE. */ if (!(block->status & BLOCK_ERROR)) {#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_unlock(&keycache->cache_lock);#endif
if (!(read_length & 511)) bmove512(block->buffer+offset, buff, read_length); else memcpy(block->buffer+offset, buff, (size_t) read_length);
#if !defined(SERIALIZED_READ_FROM_CACHE)
keycache_pthread_mutex_lock(&keycache->cache_lock);#endif
}
if (!dont_write) { /* Not used in the server. buff has been written to disk at start. */ if ((block->status & BLOCK_CHANGED) && (!offset && read_length >= keycache->key_cache_block_size)) link_to_file_list(keycache, block, block->hash_link->file, 1); } else if (! (block->status & BLOCK_CHANGED)) link_to_changed_list(keycache, block); block->status|=BLOCK_READ; /*
Allow block to be selected for to be freed. Since it is marked BLOCK_CHANGED too, it won't be selected for to be freed without a flush. */ block->status&= ~BLOCK_FOR_UPDATE; set_if_smaller(block->offset, offset); set_if_bigger(block->length, read_length+offset);
/* Threads may be waiting for the changes to be complete. */ release_whole_queue(&block->wqueue[COND_FOR_REQUESTED]);
/*
If only a part of the cache block is to be replaced, and the rest has been read from file, then the cache lock has been released for I/O and it could be possible that another thread wants to evict or free the block and waits for it to be released. So we must not just decrement hash_link->requests, but also wake a waiting thread. */ remove_reader(block);
/* Error injection for coverage testing. */ DBUG_EXECUTE_IF("key_cache_write_block_error", block->status|= BLOCK_ERROR;);
/* Do not link erroneous blocks into the LRU ring, but free them. */ if (!(block->status & BLOCK_ERROR)) { /*
Link the block into the LRU ring if it's the last submitted request for the block. This enables eviction for the block. */ unreg_request(keycache, block, 1); } else { /* Pretend a "clean" block to avoid complications. */ block->status&= ~(BLOCK_CHANGED); free_block(keycache, block); error= 1; break; }
next_block: buff+= read_length; filepos+= read_length+offset; offset= 0;
} while ((length-= read_length)); goto end; }
no_key_cache: /* Key cache is not used */ if (dont_write) { /* Used in the server. */ keycache->global_cache_w_requests++; keycache->global_cache_write++; if (locked_and_incremented) keycache_pthread_mutex_unlock(&keycache->cache_lock); if (my_pwrite(file, (uchar*) buff, length, filepos, MYF(MY_NABP | MY_WAIT_IF_FULL))) error=1; if (locked_and_incremented) keycache_pthread_mutex_lock(&keycache->cache_lock); }
end: if (locked_and_incremented) { dec_counter_for_resize_op(keycache); keycache_pthread_mutex_unlock(&keycache->cache_lock); } if (MYSQL_KEYCACHE_WRITE_DONE_ENABLED()) { MYSQL_KEYCACHE_WRITE_DONE((ulong) (keycache->blocks_used * keycache->key_cache_block_size), (ulong) (keycache->blocks_unused * keycache->key_cache_block_size)); } #if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("exec", test_key_cache(keycache, "end of key_cache_write", 1););#endif
DBUG_RETURN(error);}
/*
Free block.
SYNOPSIS free_block() keycache Pointer to a key cache data structure block Pointer to the block to free
DESCRIPTION Remove reference to block from hash table. Remove block from the chain of clean blocks. Add block to the free list.
NOTE Block must not be free (status == 0). Block must not be in free_block_list. Block must not be in the LRU ring. Block must not be in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH). Block must not be in free (BLOCK_REASSIGNED). Block must not be in flush (BLOCK_IN_FLUSH). Block must not be dirty (BLOCK_CHANGED). Block must not be in changed_blocks (dirty) hash. Block must be in file_blocks (clean) hash. Block must refer to a hash_link. Block must have a request registered on it.*/
static void free_block(KEY_CACHE *keycache, BLOCK_LINK *block){ KEYCACHE_THREAD_TRACE("free block"); KEYCACHE_DBUG_PRINT("free_block", ("block %u to be freed, hash_link %p status: %u", BLOCK_NUMBER(block), block->hash_link, block->status)); /*
Assert that the block is not free already. And that it is in a clean state. Note that the block might just be assigned to a hash_link and not yet read (BLOCK_READ may not be set here). In this case a reader is registered in the hash_link and free_block() will wait for it below. */ DBUG_ASSERT((block->status & BLOCK_IN_USE) && !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_REASSIGNED | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_FOR_UPDATE))); /* Assert that the block is in a file_blocks chain. */ DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); /* Assert that the block is not in the LRU ring. */ DBUG_ASSERT(!block->next_used && !block->prev_used); /*
IMHO the below condition (if()) makes no sense. I can't see how it could be possible that free_block() is entered with a NULL hash_link pointer. The only place where it can become NULL is in free_block() (or before its first use ever, but for those blocks free_block() is not called). I don't remove the conditional as it cannot harm, but place an DBUG_ASSERT to confirm my hypothesis. Eventually the condition (if()) can be removed. */ DBUG_ASSERT(block->hash_link && block->hash_link->block == block); if (block->hash_link) { /*
While waiting for readers to finish, new readers might request the block. But since we set block->status|= BLOCK_REASSIGNED, they will wait on block->wqueue[COND_FOR_SAVED]. They must be signalled later. */ block->status|= BLOCK_REASSIGNED; wait_for_readers(keycache, block); /*
The block must not have been freed by another thread. Repeat some checks. An additional requirement is that it must be read now (BLOCK_READ). */ DBUG_ASSERT(block->hash_link && block->hash_link->block == block); DBUG_ASSERT((block->status & (BLOCK_READ | BLOCK_IN_USE | BLOCK_REASSIGNED)) && !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_FOR_UPDATE))); DBUG_ASSERT(block->prev_changed && *block->prev_changed == block); DBUG_ASSERT(!block->prev_used); /*
Unset BLOCK_REASSIGNED again. If we hand the block to an evicting thread (through unreg_request() below), other threads must not see this flag. They could become confused. */ block->status&= ~BLOCK_REASSIGNED; /*
Do not release the hash_link until the block is off all lists. At least not if we hand it over for eviction in unreg_request(). */ }
/*
Unregister the block request and link the block into the LRU ring. This enables eviction for the block. If the LRU ring was empty and threads are waiting for a block, then the block wil be handed over for eviction immediately. Otherwise we will unlink it from the LRU ring again, without releasing the lock in between. So decrementing the request counter and updating statistics are the only relevant operation in this case. Assert that there are no other requests registered. */ DBUG_ASSERT(block->requests == 1); unreg_request(keycache, block, 0); /*
Note that even without releasing the cache lock it is possible that the block is immediately selected for eviction by link_block() and thus not added to the LRU ring. In this case we must not touch the block any more. */ if (block->status & BLOCK_IN_EVICTION) return;
/* Error blocks are not put into the LRU ring. */ if (!(block->status & BLOCK_ERROR)) { /* Here the block must be in the LRU ring. Unlink it again. */ DBUG_ASSERT(block->next_used && block->prev_used && *block->prev_used == block); unlink_block(keycache, block); } if (block->temperature == BLOCK_WARM) keycache->warm_blocks--; block->temperature= BLOCK_COLD;
/* Remove from file_blocks hash. */ unlink_changed(block);
/* Remove reference to block from hash table. */ unlink_hash(keycache, block->hash_link); block->hash_link= NULL;
block->status= 0; block->length= 0; block->offset= keycache->key_cache_block_size; KEYCACHE_THREAD_TRACE("free block"); KEYCACHE_DBUG_PRINT("free_block", ("block is freed"));
/* Enforced by unlink_changed(), but just to be sure. */ DBUG_ASSERT(!block->next_changed && !block->prev_changed); /* Enforced by unlink_block(): not in LRU ring nor in free_block_list. */ DBUG_ASSERT(!block->next_used && !block->prev_used); /* Insert the free block in the free list. */ block->next_used= keycache->free_block_list; keycache->free_block_list= block; /* Keep track of the number of currently unused blocks. */ keycache->blocks_unused++;
/* All pending requests for this page must be resubmitted. */ release_whole_queue(&block->wqueue[COND_FOR_SAVED]);}
static int cmp_sec_link(BLOCK_LINK **a, BLOCK_LINK **b){ return (((*a)->hash_link->diskpos < (*b)->hash_link->diskpos) ? -1 : ((*a)->hash_link->diskpos > (*b)->hash_link->diskpos) ? 1 : 0);}
/*
Flush a portion of changed blocks to disk, free used blocks if requested*/
static int flush_cached_blocks(KEY_CACHE *keycache, File file, BLOCK_LINK **cache, BLOCK_LINK **end, enum flush_type type){ int error; int last_errno= 0; uint count= (uint) (end-cache);
/* Don't lock the cache during the flush */ keycache_pthread_mutex_unlock(&keycache->cache_lock); /*
As all blocks referred in 'cache' are marked by BLOCK_IN_FLUSH we are guarunteed no thread will change them */ my_qsort((uchar*) cache, count, sizeof(*cache), (qsort_cmp) cmp_sec_link);
keycache_pthread_mutex_lock(&keycache->cache_lock); /*
Note: Do not break the loop. We have registered a request on every block in 'cache'. These must be unregistered by free_block() or unreg_request(). */ for ( ; cache != end ; cache++) { BLOCK_LINK *block= *cache;
KEYCACHE_DBUG_PRINT("flush_cached_blocks", ("block %u to be flushed", BLOCK_NUMBER(block))); /*
If the block contents is going to be changed, we abandon the flush for this block. flush_key_blocks_int() will restart its search and handle the block properly. */ if (!(block->status & BLOCK_FOR_UPDATE)) { /* Blocks coming here must have a certain status. */ DBUG_ASSERT(block->hash_link); DBUG_ASSERT(block->hash_link->block == block); DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT((block->status & ~BLOCK_IN_EVICTION) == (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); block->status|= BLOCK_IN_FLUSHWRITE; keycache_pthread_mutex_unlock(&keycache->cache_lock); error= my_pwrite(file, block->buffer+block->offset, block->length - block->offset, block->hash_link->diskpos+ block->offset, MYF(MY_NABP | MY_WAIT_IF_FULL)); keycache_pthread_mutex_lock(&keycache->cache_lock); keycache->global_cache_write++; if (error) { block->status|= BLOCK_ERROR; if (!last_errno) last_errno= errno ? errno : -1; } block->status&= ~BLOCK_IN_FLUSHWRITE; /* Block must not have changed status except BLOCK_FOR_UPDATE. */ DBUG_ASSERT(block->hash_link); DBUG_ASSERT(block->hash_link->block == block); DBUG_ASSERT(block->hash_link->file == file); DBUG_ASSERT((block->status & ~(BLOCK_FOR_UPDATE | BLOCK_IN_EVICTION)) == (BLOCK_READ | BLOCK_IN_FLUSH | BLOCK_CHANGED | BLOCK_IN_USE)); /*
Set correct status and link in right queue for free or later use. free_block() must not see BLOCK_CHANGED and it may need to wait for readers of the block. These should not see the block in the wrong hash. If not freeing the block, we need to have it in the right queue anyway. */ link_to_file_list(keycache, block, file, 1); } block->status&= ~BLOCK_IN_FLUSH; /*
Let to proceed for possible waiting requests to write to the block page. It might happen only during an operation to resize the key cache. */ release_whole_queue(&block->wqueue[COND_FOR_SAVED]); /* type will never be FLUSH_IGNORE_CHANGED here */ if (!(type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE) && !(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_FOR_UPDATE))) { /*
Note that a request has been registered against the block in flush_key_blocks_int(). */ free_block(keycache, block); } else { /*
Link the block into the LRU ring if it's the last submitted request for the block. This enables eviction for the block. Note that a request has been registered against the block in flush_key_blocks_int(). */ unreg_request(keycache, block, 1); }
} /* end of for ( ; cache != end ; cache++) */ return last_errno;}
/*
Flush all key blocks for a file to disk, but don't do any mutex locks.
SYNOPSIS flush_key_blocks_int() keycache pointer to a key cache data structure file handler for the file to flush to flush_type type of the flush
NOTES This function doesn't do any mutex locks because it needs to be called both from flush_key_blocks and flush_all_key_blocks (the later one does the mutex lock in the resize_key_cache() function).
We do only care about changed blocks that exist when the function is entered. We do not guarantee that all changed blocks of the file are flushed if more blocks change while this function is running.
RETURN 0 ok 1 error*/
static int flush_key_blocks_int(KEY_CACHE *keycache, File file, enum flush_type type){ BLOCK_LINK *cache_buff[FLUSH_CACHE],**cache; int last_errno= 0; int last_errcnt= 0; DBUG_ENTER("flush_key_blocks_int"); DBUG_PRINT("enter",("file: %d blocks_used: %lu blocks_changed: %lu", file, keycache->blocks_used, keycache->blocks_changed));
#if !defined(DBUG_OFF) && defined(EXTRA_DEBUG)
DBUG_EXECUTE("check_keycache", test_key_cache(keycache, "start of flush_key_blocks", 0););#endif
cache= cache_buff; if (keycache->disk_blocks > 0 && (!my_disable_flush_key_blocks || type != FLUSH_KEEP)) { /* Key cache exists and flush is not disabled */ int error= 0; uint count= FLUSH_CACHE; BLOCK_LINK **pos,**end; BLOCK_LINK *first_in_switch= NULL; BLOCK_LINK *last_in_flush; BLOCK_LINK *last_for_update; BLOCK_LINK *block, *next;#if defined(KEYCACHE_DEBUG)
uint cnt=0;#endif
if (type != FLUSH_IGNORE_CHANGED) { /*
Count how many key blocks we have to cache to be able to flush all dirty pages with minimum seek moves */ count= 0; for (block= keycache->changed_blocks[FILE_HASH(file)] ; block ; block= block->next_changed) { if ((block->hash_link->file == file) && !(block->status & BLOCK_IN_FLUSH)) { count++; KEYCACHE_DBUG_ASSERT(count<= keycache->blocks_used); } } /*
Allocate a new buffer only if its bigger than the one we have. Assure that we always have some entries for the case that new changed blocks appear while we need to wait for something. */ if ((count > FLUSH_CACHE) && !(cache= (BLOCK_LINK**) my_malloc(sizeof(BLOCK_LINK*)*count, MYF(0)))) cache= cache_buff; /*
After a restart there could be more changed blocks than now. So we should not let count become smaller than the fixed buffer. */ if (cache == cache_buff) count= FLUSH_CACHE; }
/* Retrieve the blocks and write them to a buffer to be flushed */restart: last_in_flush= NULL; last_for_update= NULL; end= (pos= cache)+count; for (block= keycache->changed_blocks[FILE_HASH(file)] ; block ; block= next) {#if defined(KEYCACHE_DEBUG)
cnt++; KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);#endif
next= block->next_changed; if (block->hash_link->file == file) { if (!(block->status & (BLOCK_IN_FLUSH | BLOCK_FOR_UPDATE))) { /*
Note: The special handling of BLOCK_IN_SWITCH is obsolete since we set BLOCK_IN_FLUSH if the eviction includes a flush. It can be removed in a later version. */ if (!(block->status & BLOCK_IN_SWITCH)) { /*
We care only for the blocks for which flushing was not initiated by another thread and which are not in eviction. Registering a request on the block unlinks it from the LRU ring and protects against eviction. */ reg_requests(keycache, block, 1); if (type != FLUSH_IGNORE_CHANGED) { /* It's not a temporary file */ if (pos == end) { /*
This should happen relatively seldom. Remove the request because we won't do anything with the block but restart and pick it again in the next iteration. */ unreg_request(keycache, block, 0); /*
This happens only if there is not enough memory for the big block */ if ((error= flush_cached_blocks(keycache, file, cache, end,type))) { /* Do not loop infinitely trying to flush in vain. */ if ((last_errno == error) && (++last_errcnt > 5)) goto err; last_errno= error; } /*
Restart the scan as some other thread might have changed the changed blocks chain: the blocks that were in switch state before the flush started have to be excluded */ goto restart; } /*
Mark the block with BLOCK_IN_FLUSH in order not to let other threads to use it for new pages and interfere with our sequence of flushing dirty file pages. We must not set this flag before actually putting the block on the write burst array called 'cache'. */ block->status|= BLOCK_IN_FLUSH; /* Add block to the array for a write burst. */ *pos++= block; } else { /* It's a temporary file */ DBUG_ASSERT(!(block->status & BLOCK_REASSIGNED)); /*
free_block() must not be called with BLOCK_CHANGED. Note that we must not change the BLOCK_CHANGED flag outside of link_to_file_list() so that it is always in the correct queue and the *blocks_changed counters are correct. */ link_to_file_list(keycache, block, file, 1); if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH))) { /* A request has been registered against the block above. */ free_block(keycache, block); } else { /*
Link the block into the LRU ring if it's the last submitted request for the block. This enables eviction for the block. A request has been registered against the block above. */ unreg_request(keycache, block, 1); } } } else { /*
Link the block into a list of blocks 'in switch'.
WARNING: Here we introduce a place where a changed block is not in the changed_blocks hash! This is acceptable for a BLOCK_IN_SWITCH. Never try this for another situation. Other parts of the key cache code rely on changed blocks being in the changed_blocks hash. */ unlink_changed(block); link_changed(block, &first_in_switch); } } else if (type != FLUSH_KEEP) { /*
During the normal flush at end of statement (FLUSH_KEEP) we do not need to ensure that blocks in flush or update by other threads are flushed. They will be flushed by them later. In all other cases we must assure that we do not have any changed block of this file in the cache when this function returns. */ if (block->status & BLOCK_IN_FLUSH) { /* Remember the last block found to be in flush. */ last_in_flush= block; } else { /* Remember the last block found to be selected for update. */ last_for_update= block; } } } } if (pos != cache) { if ((error= flush_cached_blocks(keycache, file, cache, pos, type))) { /* Do not loop inifnitely trying to flush in vain. */ if ((last_errno == error) && (++last_errcnt > 5)) goto err; last_errno= error; } /*
Do not restart here during the normal flush at end of statement (FLUSH_KEEP). We have now flushed at least all blocks that were changed when entering this function. In all other cases we must assure that we do not have any changed block of this file in the cache when this function returns. */ if (type != FLUSH_KEEP) goto restart; } if (last_in_flush) { /*
There are no blocks to be flushed by this thread, but blocks in flush by other threads. Wait until one of the blocks is flushed. Re-check the condition for last_in_flush. We may have unlocked the cache_lock in flush_cached_blocks(). The state of the block could have changed. */ if (last_in_flush->status & BLOCK_IN_FLUSH) wait_on_queue(&last_in_flush->wqueue[COND_FOR_SAVED], &keycache->cache_lock); /* Be sure not to lose a block. They may be flushed in random order. */ goto restart; } if (last_for_update) { /*
There are no blocks to be flushed by this thread, but blocks for update by other threads. Wait until one of the blocks is updated. Re-check the condition for last_for_update. We may have unlocked the cache_lock in flush_cached_blocks(). The state of the block could have changed. */ if (last_for_update->status & BLOCK_FOR_UPDATE) wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); /* The block is now changed. Flush it. */ goto restart; }
/*
Wait until the list of blocks in switch is empty. The threads that are switching these blocks will relink them to clean file chains while we wait and thus empty the 'first_in_switch' chain. */ while (first_in_switch) {#if defined(KEYCACHE_DEBUG)
cnt= 0;#endif
wait_on_queue(&first_in_switch->wqueue[COND_FOR_SAVED], &keycache->cache_lock);#if defined(KEYCACHE_DEBUG)
cnt++; KEYCACHE_DBUG_ASSERT(cnt <= keycache->blocks_used);#endif
/*
Do not restart here. We have flushed all blocks that were changed when entering this function and were not marked for eviction. Other threads have now flushed all remaining blocks in the course of their eviction. */ }
if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) { BLOCK_LINK *last_for_update= NULL; BLOCK_LINK *last_in_switch= NULL; uint total_found= 0; uint found;
/*
Finally free all clean blocks for this file. During resize this may be run by two threads in parallel. */ do { found= 0; for (block= keycache->file_blocks[FILE_HASH(file)] ; block ; block= next) { /* Remember the next block. After freeing we cannot get at it. */ next= block->next_changed;
/* Changed blocks cannot appear in the file_blocks hash. */ DBUG_ASSERT(!(block->status & BLOCK_CHANGED)); if (block->hash_link->file == file) { /* We must skip blocks that will be changed. */ if (block->status & BLOCK_FOR_UPDATE) { last_for_update= block; continue; }
/*
We must not free blocks in eviction (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH) or blocks intended to be freed (BLOCK_REASSIGNED). */ if (!(block->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_REASSIGNED))) { struct st_hash_link *next_hash_link; my_off_t next_diskpos; File next_file; uint next_status; uint hash_requests;
total_found++; found++; KEYCACHE_DBUG_ASSERT(found <= keycache->blocks_used);
/*
Register a request. This unlinks the block from the LRU ring and protects it against eviction. This is required by free_block(). */ reg_requests(keycache, block, 1);
/*
free_block() may need to wait for readers of the block. This is the moment where the other thread can move the 'next' block from the chain. free_block() needs to wait if there are requests for the block pending. */ if (next && (hash_requests= block->hash_link->requests)) { /* Copy values from the 'next' block and its hash_link. */ next_status= next->status; next_hash_link= next->hash_link; next_diskpos= next_hash_link->diskpos; next_file= next_hash_link->file; DBUG_ASSERT(next == next_hash_link->block); }
free_block(keycache, block); /*
If we had to wait and the state of the 'next' block changed, break the inner loop. 'next' may no longer be part of the current chain.
We do not want to break the loop after every free_block(), not even only after waits. The chain might be quite long and contain blocks for many files. Traversing it again and again to find more blocks for this file could become quite inefficient. */ if (next && hash_requests && ((next_status != next->status) || (next_hash_link != next->hash_link) || (next_file != next_hash_link->file) || (next_diskpos != next_hash_link->diskpos) || (next != next_hash_link->block))) break; } else { last_in_switch= block; } } } /* end for block in file_blocks */ } while (found);
/*
If any clean block has been found, we may have waited for it to become free. In this case it could be possible that another clean block became dirty. This is possible if the write request existed before the flush started (BLOCK_FOR_UPDATE). Re-check the hashes. */ if (total_found) goto restart;
/*
To avoid an infinite loop, wait until one of the blocks marked for update is updated. */ if (last_for_update) { /* We did not wait. Block must not have changed status. */ DBUG_ASSERT(last_for_update->status & BLOCK_FOR_UPDATE); wait_on_queue(&last_for_update->wqueue[COND_FOR_REQUESTED], &keycache->cache_lock); goto restart; }
/*
To avoid an infinite loop wait until one of the blocks marked for eviction is switched. */ if (last_in_switch) { /* We did not wait. Block must not have changed status. */ DBUG_ASSERT(last_in_switch->status & (BLOCK_IN_EVICTION | BLOCK_IN_SWITCH | BLOCK_REASSIGNED)); wait_on_queue(&last_in_switch->wqueue[COND_FOR_SAVED], &keycache->cache_lock); goto restart; }
} /* if (! (type == FLUSH_KEEP || type == FLUSH_FORCE_WRITE)) */
} /* if (keycache->disk_blocks > 0 */
#ifndef DBUG_OFF
DBUG_EXECUTE("check_keycache", test_key_cache(keycache, "end of flush_key_blocks", 0););#endif
err: if (cache != cache_buff) my_free(cache); if (last_errno) errno=last_errno; /* Return first error */ DBUG_RETURN(last_errno != 0);}
/*
Flush all blocks for a file to disk
SYNOPSIS
flush_key_blocks() keycache pointer to a key cache data structure file handler for the file to flush to flush_type type of the flush
RETURN 0 ok 1 error*/
int flush_key_blocks(KEY_CACHE *keycache, File file, enum flush_type type){ int res= 0; DBUG_ENTER("flush_key_blocks"); DBUG_PRINT("enter", ("keycache: 0x%lx", (long) keycache));
if (!keycache->key_cache_inited) DBUG_RETURN(0);
keycache_pthread_mutex_lock(&keycache->cache_lock); /* While waiting for lock, keycache could have been ended. */ if (keycache->disk_blocks > 0) { inc_counter_for_resize_op(keycache); res= flush_key_blocks_int(keycache, file, type); dec_counter_for_resize_op(keycache); } keycache_pthread_mutex_unlock(&keycache->cache_lock); DBUG_RETURN(res);}
/*
Flush all blocks in the key cache to disk.
SYNOPSIS flush_all_key_blocks() keycache pointer to key cache root structure
DESCRIPTION
Flushing of the whole key cache is done in two phases.
1. Flush all changed blocks, waiting for them if necessary. Loop until there is no changed block left in the cache.
2. Free all clean blocks. Normally this means free all blocks. The changed blocks were flushed in phase 1 and became clean. However we may need to wait for blocks that are read by other threads. While we wait, a clean block could become changed if that operation started before the resize operation started. To be safe we must restart at phase 1.
When we can run through the changed_blocks and file_blocks hashes without finding a block any more, then we are done.
Note that we hold keycache->cache_lock all the time unless we need to wait for something.
RETURN 0 OK != 0 Error*/
static int flush_all_key_blocks(KEY_CACHE *keycache){ BLOCK_LINK *block; uint total_found; uint found; uint idx; DBUG_ENTER("flush_all_key_blocks");
do { mysql_mutex_assert_owner(&keycache->cache_lock); total_found= 0;
/*
Phase1: Flush all changed blocks, waiting for them if necessary. Loop until there is no changed block left in the cache. */ do { found= 0; /* Step over the whole changed_blocks hash array. */ for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) { /*
If an array element is non-empty, use the first block from its chain to find a file for flush. All changed blocks for this file are flushed. So the same block will not appear at this place again with the next iteration. New writes for blocks are not accepted during the flush. If multiple files share the same hash bucket, one of them will be flushed per iteration of the outer loop of phase 1. */ if ((block= keycache->changed_blocks[idx])) { found++; /*
Flush dirty blocks but do not free them yet. They can be used for reading until all other blocks are flushed too. */ if (flush_key_blocks_int(keycache, block->hash_link->file, FLUSH_FORCE_WRITE)) DBUG_RETURN(1); } }
} while (found);
/*
Phase 2: Free all clean blocks. Normally this means free all blocks. The changed blocks were flushed in phase 1 and became clean. However we may need to wait for blocks that are read by other threads. While we wait, a clean block could become changed if that operation started before the resize operation started. To be safe we must restart at phase 1. */ do { found= 0; /* Step over the whole file_blocks hash array. */ for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) { /*
If an array element is non-empty, use the first block from its chain to find a file for flush. All blocks for this file are freed. So the same block will not appear at this place again with the next iteration. If multiple files share the same hash bucket, one of them will be flushed per iteration of the outer loop of phase 2. */ if ((block= keycache->file_blocks[idx])) { total_found++; found++; if (flush_key_blocks_int(keycache, block->hash_link->file, FLUSH_RELEASE)) DBUG_RETURN(1); } }
} while (found);
/*
If any clean block has been found, we may have waited for it to become free. In this case it could be possible that another clean block became dirty. This is possible if the write request existed before the resize started (BLOCK_FOR_UPDATE). Re-check the hashes. */ } while (total_found);
#ifndef DBUG_OFF
/* Now there should not exist any block any more. */ for (idx= 0; idx < CHANGED_BLOCKS_HASH; idx++) { DBUG_ASSERT(!keycache->changed_blocks[idx]); DBUG_ASSERT(!keycache->file_blocks[idx]); }#endif
DBUG_RETURN(0);}
/*
Reset the counters of a key cache.
SYNOPSIS reset_key_cache_counters() name the name of a key cache key_cache pointer to the key kache to be reset
DESCRIPTION This procedure is used by process_key_caches() to reset the counters of all currently used key caches, both the default one and the named ones.
RETURN 0 on success (always because it can't fail)*/
int reset_key_cache_counters(const char *name __attribute__((unused)), KEY_CACHE *key_cache){ DBUG_ENTER("reset_key_cache_counters"); if (!key_cache->key_cache_inited) { DBUG_PRINT("info", ("Key cache %s not initialized.", name)); DBUG_RETURN(0); } DBUG_PRINT("info", ("Resetting counters for key cache %s.", name));
key_cache->global_blocks_changed= 0; /* Key_blocks_not_flushed */ key_cache->global_cache_r_requests= 0; /* Key_read_requests */ key_cache->global_cache_read= 0; /* Key_reads */ key_cache->global_cache_w_requests= 0; /* Key_write_requests */ key_cache->global_cache_write= 0; /* Key_writes */ DBUG_RETURN(0);}
#ifndef DBUG_OFF
/*
Test if disk-cache is ok*/static void test_key_cache(KEY_CACHE *keycache __attribute__((unused)), const char *where __attribute__((unused)), my_bool lock __attribute__((unused))){ /* TODO */}#endif
#if defined(KEYCACHE_TIMEOUT)
#define KEYCACHE_DUMP_FILE "keycache_dump.txt"
#define MAX_QUEUE_LEN 100
static void keycache_dump(KEY_CACHE *keycache){ FILE *keycache_dump_file=fopen(KEYCACHE_DUMP_FILE, "w"); struct st_my_thread_var *last; struct st_my_thread_var *thread; BLOCK_LINK *block; HASH_LINK *hash_link; KEYCACHE_PAGE *page; uint i;
fprintf(keycache_dump_file, "thread:%u\n", thread->id);
i=0; thread=last=waiting_for_hash_link.last_thread; fprintf(keycache_dump_file, "queue of threads waiting for hash link\n"); if (thread) do { thread=thread->next; page= (KEYCACHE_PAGE *) thread->opt_info; fprintf(keycache_dump_file, "thread:%u, (file,filepos)=(%u,%lu)\n", thread->id,(uint) page->file,(ulong) page->filepos); if (++i == MAX_QUEUE_LEN) break; } while (thread != last);
i=0; thread=last=waiting_for_block.last_thread; fprintf(keycache_dump_file, "queue of threads waiting for block\n"); if (thread) do { thread=thread->next; hash_link= (HASH_LINK *) thread->opt_info; fprintf(keycache_dump_file, "thread:%u hash_link:%u (file,filepos)=(%u,%lu)\n", thread->id, (uint) HASH_LINK_NUMBER(hash_link), (uint) hash_link->file,(ulong) hash_link->diskpos); if (++i == MAX_QUEUE_LEN) break; } while (thread != last);
for (i=0 ; i< keycache->blocks_used ; i++) { int j; block= &keycache->block_root[i]; hash_link= block->hash_link; fprintf(keycache_dump_file, "block:%u hash_link:%d status:%x #requests=%u waiting_for_readers:%d\n", i, (int) (hash_link ? HASH_LINK_NUMBER(hash_link) : -1), block->status, block->requests, block->condvar ? 1 : 0); for (j=0 ; j < 2; j++) { KEYCACHE_WQUEUE *wqueue=&block->wqueue[j]; thread= last= wqueue->last_thread; fprintf(keycache_dump_file, "queue #%d\n", j); if (thread) { do { thread=thread->next; fprintf(keycache_dump_file, "thread:%u\n", thread->id); if (++i == MAX_QUEUE_LEN) break; } while (thread != last); } } } fprintf(keycache_dump_file, "LRU chain:"); block= keycache= used_last; if (block) { do { block= block->next_used; fprintf(keycache_dump_file, "block:%u, ", BLOCK_NUMBER(block)); } while (block != keycache->used_last); } fprintf(keycache_dump_file, "\n");
fclose(keycache_dump_file);}
#endif /* defined(KEYCACHE_TIMEOUT) */
#if defined(KEYCACHE_TIMEOUT) && !defined(__WIN__)
static int keycache_pthread_cond_wait(mysql_cond_t *cond, mysql_mutex_t *mutex){ int rc; struct timeval now; /* time when we started waiting */ struct timespec timeout; /* timeout value for the wait function */ struct timezone tz;#if defined(KEYCACHE_DEBUG)
int cnt=0;#endif
/* Get current time */ gettimeofday(&now, &tz); /* Prepare timeout value */ timeout.tv_sec= now.tv_sec + KEYCACHE_TIMEOUT; /*
timeval uses microseconds. timespec uses nanoseconds. 1 nanosecond = 1000 micro seconds */ timeout.tv_nsec= now.tv_usec * 1000; KEYCACHE_THREAD_TRACE_END("started waiting");#if defined(KEYCACHE_DEBUG)
cnt++; if (cnt % 100 == 0) fprintf(keycache_debug_log, "waiting...\n"); fflush(keycache_debug_log);#endif
rc= mysql_cond_timedwait(cond, mutex, &timeout); KEYCACHE_THREAD_TRACE_BEGIN("finished waiting"); if (rc == ETIMEDOUT || rc == ETIME) {#if defined(KEYCACHE_DEBUG)
fprintf(keycache_debug_log,"aborted by keycache timeout\n"); fclose(keycache_debug_log); abort();#endif
keycache_dump(); }
#if defined(KEYCACHE_DEBUG)
KEYCACHE_DBUG_ASSERT(rc != ETIMEDOUT);#else
assert(rc != ETIMEDOUT);#endif
return rc;}#else
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_cond_wait(mysql_cond_t *cond, mysql_mutex_t *mutex){ int rc; KEYCACHE_THREAD_TRACE_END("started waiting"); rc= mysql_cond_wait(cond, mutex); KEYCACHE_THREAD_TRACE_BEGIN("finished waiting"); return rc;}#endif
#endif /* defined(KEYCACHE_TIMEOUT) && !defined(__WIN__) */
#if defined(KEYCACHE_DEBUG)
static int keycache_pthread_mutex_lock(mysql_mutex_t *mutex){ int rc; rc= mysql_mutex_lock(mutex); KEYCACHE_THREAD_TRACE_BEGIN(""); return rc;}
static void keycache_pthread_mutex_unlock(mysql_mutex_t *mutex){ KEYCACHE_THREAD_TRACE_END(""); mysql_mutex_unlock(mutex);}
static int keycache_pthread_cond_signal(mysql_cond_t *cond){ int rc; KEYCACHE_THREAD_TRACE("signal"); rc= mysql_cond_signal(cond); return rc;}
#if defined(KEYCACHE_DEBUG_LOG)
static void keycache_debug_print(const char * fmt,...){ va_list args; va_start(args,fmt); if (keycache_debug_log) { (void) vfprintf(keycache_debug_log, fmt, args); (void) fputc('\n',keycache_debug_log); } va_end(args);}#endif /* defined(KEYCACHE_DEBUG_LOG) */
#if defined(KEYCACHE_DEBUG_LOG)
void keycache_debug_log_close(void){ if (keycache_debug_log) fclose(keycache_debug_log);}#endif /* defined(KEYCACHE_DEBUG_LOG) */
#endif /* defined(KEYCACHE_DEBUG) */
#if !defined(DBUG_OFF)
#define F_B_PRT(_f_, _v_) DBUG_PRINT("assert_fail", (_f_, _v_))
static int fail_block(BLOCK_LINK *block){ F_B_PRT("block->next_used: %lx\n", (ulong) block->next_used); F_B_PRT("block->prev_used: %lx\n", (ulong) block->prev_used); F_B_PRT("block->next_changed: %lx\n", (ulong) block->next_changed); F_B_PRT("block->prev_changed: %lx\n", (ulong) block->prev_changed); F_B_PRT("block->hash_link: %lx\n", (ulong) block->hash_link); F_B_PRT("block->status: %u\n", block->status); F_B_PRT("block->length: %u\n", block->length); F_B_PRT("block->offset: %u\n", block->offset); F_B_PRT("block->requests: %u\n", block->requests); F_B_PRT("block->temperature: %u\n", block->temperature); return 0; /* Let the assert fail. */}
static int fail_hlink(HASH_LINK *hlink){ F_B_PRT("hlink->next: %lx\n", (ulong) hlink->next); F_B_PRT("hlink->prev: %lx\n", (ulong) hlink->prev); F_B_PRT("hlink->block: %lx\n", (ulong) hlink->block); F_B_PRT("hlink->diskpos: %lu\n", (ulong) hlink->diskpos); F_B_PRT("hlink->file: %d\n", hlink->file); return 0; /* Let the assert fail. */}
static int cache_empty(KEY_CACHE *keycache){ int errcnt= 0; int idx; if (keycache->disk_blocks <= 0) return 1; for (idx= 0; idx < keycache->disk_blocks; idx++) { BLOCK_LINK *block= keycache->block_root + idx; if (block->status || block->requests || block->hash_link) { fprintf(stderr, "block index: %u\n", idx); fail_block(block); errcnt++; } } for (idx= 0; idx < keycache->hash_links; idx++) { HASH_LINK *hash_link= keycache->hash_link_root + idx; if (hash_link->requests || hash_link->block) { fprintf(stderr, "hash_link index: %u\n", idx); fail_hlink(hash_link); errcnt++; } } if (errcnt) { fprintf(stderr, "blocks: %d used: %lu\n", keycache->disk_blocks, keycache->blocks_used); fprintf(stderr, "hash_links: %d used: %d\n", keycache->hash_links, keycache->hash_links_used); fprintf(stderr, "\n"); } return !errcnt;}#endif
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