branches/zip: Make innodb_thread_concurrency=0 the default.

The old default was 8.

ChangeLog

@@ -1,3 +1,11 @@
+2009-02-11	The InnoDB Team
+
+	* handler/ha_innodb.cc:
+	Make innodb_thread_concurrency=0 the default.  The old default
+	value was 8.  A non-zero setting may be useful when InnoDB is
+	showing severe scalability problems under multiple concurrent
+	connections.
+
 2009-02-10	The InnoDB Team
 
 	* handler/ha_innodb.h, handler/ha_innodb.cc:

handler/ha_innodb.cc

@@ -9682,7 +9682,7 @@ static MYSQL_SYSVAR_ULONG(sync_spin_loops, srv_n_spin_wait_rounds,
 static MYSQL_SYSVAR_ULONG(thread_concurrency, srv_thread_concurrency,
   PLUGIN_VAR_RQCMDARG,
   "Helps in performance tuning in heavily concurrent environments. Sets the maximum number of threads allowed inside InnoDB. Value 0 will disable the thread throttling.",
-  NULL, NULL, 8, 0, 1000, 0);
+  NULL, NULL, 0, 0, 1000, 0);
 
 static MYSQL_SYSVAR_ULONG(thread_sleep_delay, srv_thread_sleep_delay,
   PLUGIN_VAR_RQCMDARG,

mysql-test/innodb.result

@@ -1783,7 +1783,7 @@ Variable_name	Value
 innodb_sync_spin_loops	20
 show variables like "innodb_thread_concurrency";
 Variable_name	Value
-innodb_thread_concurrency	8
+innodb_thread_concurrency	0
 set global innodb_thread_concurrency=1001;
 Warnings:
 Warning	1292	Truncated incorrect thread_concurrency value: '1001'