branches/zip: Introduce UNIV_LRU_DEBUG for debugging the LRU buffer pool

cache, especially buf_pool->LRU_old and bpage->old.

buf_LRU_old_adjust_len(), buf_LRU_remove_block(): Check that blocks in
buf_pool->LRU_old have the "old" flag set and the blocks preceding
buf_pool->LRU_old have the "old" flag clear.

buf_LRU_add_block_low(), buf_relocate(): Check that buf_pool->LRU_old
is the first block in the LRU list whose "old" flag is set.

buf_LRU_free_block(): When replacing a control block in the LRU list
with a control block for a compressed page, assert that the "old"
flags in the neighboring LRU list entries grow monotonically.

buf_page_set_old(): Assert that the "old" flags in the neighboring LRU
list entries grow monotonically.

buf/buf0buf.c

@@ -1053,6 +1053,14 @@ buf_relocate(
 
 	if (UNIV_UNLIKELY(buf_pool->LRU_old == bpage)) {
 		buf_pool->LRU_old = dpage;
+#ifdef UNIV_LRU_DEBUG
+		/* buf_pool->LRU_old must be the first item in the LRU list
+		whose "old" flag is set. */
+		ut_a(!UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)
+		     || !UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)->old);
+		ut_a(!UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)
+		     || UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)->old);
+#endif /* UNIV_LRU_DEBUG */
 	}
 
 	ut_d(UT_LIST_VALIDATE(LRU, buf_page_t, buf_pool->LRU));

buf/buf0lru.c

@@ -790,12 +790,25 @@ buf_LRU_old_adjust_len(void)
 #if 3 * (BUF_LRU_OLD_MIN_LEN / 8) <= BUF_LRU_OLD_TOLERANCE + 5
 # error "3 * (BUF_LRU_OLD_MIN_LEN / 8) <= BUF_LRU_OLD_TOLERANCE + 5"
 #endif
+#ifdef UNIV_LRU_DEBUG
+	/* buf_pool->LRU_old must be the first item in the LRU list
+	whose "old" flag is set. */
+	ut_a(buf_pool->LRU_old->old);
+	ut_a(!UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)
+	     || !UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)->old);
+	ut_a(!UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)
+	     || UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)->old);
+#endif /* UNIV_LRU_DEBUG */
 
 	for (;;) {
 		old_len = buf_pool->LRU_old_len;
 		new_len = 3 * (UT_LIST_GET_LEN(buf_pool->LRU) / 8);
 
 		ut_ad(buf_pool->LRU_old->in_LRU_list);
+		ut_a(buf_pool->LRU_old);
+#ifdef UNIV_LRU_DEBUG
+		ut_a(buf_pool->LRU_old->old);
+#endif /* UNIV_LRU_DEBUG */
 
 		/* Update the LRU_old pointer if necessary */
 
@@ -803,6 +816,9 @@ buf_LRU_old_adjust_len(void)
 
 			buf_pool->LRU_old = UT_LIST_GET_PREV(
 				LRU, buf_pool->LRU_old);
+#ifdef UNIV_LRU_DEBUG
+			ut_a(!buf_pool->LRU_old->old);
+#endif /* UNIV_LRU_DEBUG */
 			buf_page_set_old(buf_pool->LRU_old, TRUE);
 			buf_pool->LRU_old_len++;
 
@@ -813,8 +829,6 @@ buf_LRU_old_adjust_len(void)
 				LRU, buf_pool->LRU_old);
 			buf_pool->LRU_old_len--;
 		} else {
-			ut_a(buf_pool->LRU_old); /* Check that we did not
-						 fall out of the LRU list */
 			return;
 		}
 	}
@@ -901,6 +915,9 @@ buf_LRU_remove_block(
 
 		buf_pool->LRU_old = UT_LIST_GET_PREV(LRU, bpage);
 		ut_a(buf_pool->LRU_old);
+#ifdef UNIV_LRU_DEBUG
+		ut_a(!buf_pool->LRU_old->old);
+#endif /* UNIV_LRU_DEBUG */
 		buf_page_set_old(buf_pool->LRU_old, TRUE);
 
 		buf_pool->LRU_old_len++;
@@ -1042,6 +1059,15 @@ buf_LRU_add_block_low(
 		bpage->LRU_position = buf_pool_clock_tic();
 		bpage->freed_page_clock = buf_pool->freed_page_clock;
 	} else {
+#ifdef UNIV_LRU_DEBUG
+		/* buf_pool->LRU_old must be the first item in the LRU list
+		whose "old" flag is set. */
+		ut_a(buf_pool->LRU_old->old);
+		ut_a(!UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)
+		     || !UT_LIST_GET_PREV(LRU, buf_pool->LRU_old)->old);
+		ut_a(!UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)
+		     || UT_LIST_GET_NEXT(LRU, buf_pool->LRU_old)->old);
+#endif /* UNIV_LRU_DEBUG */
 		UT_LIST_INSERT_AFTER(LRU, buf_pool->LRU, buf_pool->LRU_old,
 				     bpage);
 		buf_pool->LRU_old_len++;
@@ -1252,6 +1278,15 @@ alloc:
 
 						buf_pool->LRU_old = b;
 					}
+#ifdef UNIV_LRU_DEBUG
+					ut_a(prev_b->old
+					     || !UT_LIST_GET_NEXT(LRU, b)
+					     || UT_LIST_GET_NEXT(LRU, b)->old);
+				} else {
+					ut_a(!prev_b->old
+					     || !UT_LIST_GET_NEXT(LRU, b)
+					     || !UT_LIST_GET_NEXT(LRU, b)->old);
+#endif /* UNIV_LRU_DEBUG */
 				}
 
 				lru_len = UT_LIST_GET_LEN(buf_pool->LRU);

include/buf0buf.ic

@@ -446,6 +446,14 @@ buf_page_set_old(
 	ut_ad(buf_pool_mutex_own());
 	ut_ad(bpage->in_LRU_list);
 
+#ifdef UNIV_LRU_DEBUG
+	if (UT_LIST_GET_PREV(LRU, bpage) && UT_LIST_GET_NEXT(LRU, bpage)
+	    && UT_LIST_GET_PREV(LRU, bpage)->old
+	    == UT_LIST_GET_NEXT(LRU, bpage)->old) {
+		ut_a(UT_LIST_GET_PREV(LRU, bpage)->old == old);
+	}
+#endif /* UNIV_LRU_DEBUG */
+
 	bpage->old = old;
 }
 

include/univ.i

@@ -137,6 +137,7 @@ command. Not tested on Windows. */
 #define UNIV_DEBUG_FILE_ACCESSES		/* Debug .ibd file access
 						(field file_page_was_freed
 						in buf_page_t) */
+#define UNIV_LRU_DEBUG				/* debug the buffer pool LRU */
 #define UNIV_HASH_DEBUG				/* debug HASH_ macros */
 #define UNIV_LIST_DEBUG				/* debug UT_LIST_ macros */
 #define UNIV_MEM_DEBUG				/* detect memory leaks etc */