Applied innodb-5.1-ss1004

Fixes:
- Bug #15815: Very poor performance with multiple queries running concurrently
- Bug #22868: 'Thread thrashing' with > 50 concurrent conns under an upd-intensive workloadw
- Bug #24089: Race condition in fil_flush_file_spaces()


storage/innobase/btr/btr0btr.c:
  Applied innodb-5.1-ss1004
  
  Revision r934:
  btr_lift_page_up(): Set new page levels in all ancestor pages, not just
  in the father page.
  
  btr0btr.h: Add a BTR_MAX_LEVELS define.
storage/innobase/buf/buf0buf.c:
  Applied innodb-5.1-ss1004
  
  Revision r999:
  Reduce buffer pool mutex contention under >= 4 big concurrent
  CPU-bound SELECT queries.  (Bug #22868)
  
  Fix: replace the mutex by one mutex protecting the 'flush list'
  (and the free list) and several mutexes protecting portions of the
  buffer pool, where we keep several indivudual LRU lists of pages.
  
  This patch is from Sunny Bains and Heikki Tuuri.
storage/innobase/buf/buf0flu.c:
  Applied innodb-5.1-ss1004
  
  Revision r999:
  Reduce buffer pool mutex contention under >= 4 big concurrent
  CPU-bound SELECT queries.  (Bug #22868)
  
  Fix: replace the mutex by one mutex protecting the 'flush list'
  (and the free list) and several mutexes protecting portions of the
  buffer pool, where we keep several indivudual LRU lists of pages.
  
  This patch is from Sunny Bains and Heikki Tuuri.
storage/innobase/buf/buf0lru.c:
  Applied innodb-5.1-ss1004
  
  Revision r999:
  Reduce buffer pool mutex contention under >= 4 big concurrent
  CPU-bound SELECT queries.  (Bug #22868)
  
  Fix: replace the mutex by one mutex protecting the 'flush list'
  (and the free list) and several mutexes protecting portions of the
  buffer pool, where we keep several indivudual LRU lists of pages.
  
  This patch is from Sunny Bains and Heikki Tuuri.
  
  
  Revision r1004:
  UT_LIST_REMOVE(): Invalidate the node pointers #ifdef UNIV_DEBUG.
  
  buf_LRU_invalidate_tablespace(): Invoke UT_LIST_GET_PREV(LRU, block)
  before UT_LIST_REMOVE(LRU, buf_pool->LRU, block).
storage/innobase/dict/dict0crea.c:
  Applied innodb-5.1-ss1004
  
  Revision r973:
  Do not break the latching order in TRUNCATE TABLE.
  
  dict_truncate_index_tree(): Replace parameter rec_t* rec with
  btr_pcur_t* pcur.  Reposition pcur before calling btr_create().
  
  sync_thread_add_level(): Remove the relaxation of the assertion added in r968.
storage/innobase/fil/fil0fil.c:
  Applied innodb-5.1-ss1004
  
  Revision r1002:
  fil_flush_file_spaces(): Copy the system->unflushed_spaces list to an
  array while holding the mutex.  This removes the crash-triggering
  race condition that was introduced when fixing Bug 15653.  (Bug #24089)
storage/innobase/include/btr0btr.h:
  Applied innodb-5.1-ss1004
  
  Revision r934:
  btr_lift_page_up(): Set new page levels in all ancestor pages, not just
  in the father page.
  
  btr0btr.h: Add a BTR_MAX_LEVELS define.
storage/innobase/include/buf0buf.h:
  Applied innodb-5.1-ss1004
  
  Revision r999:
  Reduce buffer pool mutex contention under >= 4 big concurrent
  CPU-bound SELECT queries.  (Bug #22868)
  
  Fix: replace the mutex by one mutex protecting the 'flush list'
  (and the free list) and several mutexes protecting portions of the
  buffer pool, where we keep several indivudual LRU lists of pages.
  
  This patch is from Sunny Bains and Heikki Tuuri.
storage/innobase/include/buf0buf.ic:
  Applied innodb-5.1-ss1004
  
  Revision r999:
  Reduce buffer pool mutex contention under >= 4 big concurrent
  CPU-bound SELECT queries.  (Bug #22868)
  
  Fix: replace the mutex by one mutex protecting the 'flush list'
  (and the free list) and several mutexes protecting portions of the
  buffer pool, where we keep several indivudual LRU lists of pages.
  
  This patch is from Sunny Bains and Heikki Tuuri.
storage/innobase/include/dict0crea.h:
  Applied innodb-5.1-ss1004
  
  Revision r973:
  Do not break the latching order in TRUNCATE TABLE.
  
  dict_truncate_index_tree(): Replace parameter rec_t* rec with
  btr_pcur_t* pcur.  Reposition pcur before calling btr_create().
  
  sync_thread_add_level(): Remove the relaxation of the assertion added in r968.
storage/innobase/include/ut0lst.h:
  Applied innodb-5.1-ss1004
  
  Revision r1004:
  UT_LIST_REMOVE(): Invalidate the node pointers #ifdef UNIV_DEBUG.
  
  buf_LRU_invalidate_tablespace(): Invoke UT_LIST_GET_PREV(LRU, block)
  before UT_LIST_REMOVE(LRU, buf_pool->LRU, block).
storage/innobase/row/row0mysql.c:
  Applied innodb-5.1-ss1004
  
  Revision r973:
  Do not break the latching order in TRUNCATE TABLE.
  
  dict_truncate_index_tree(): Replace parameter rec_t* rec with
  btr_pcur_t* pcur.  Reposition pcur before calling btr_create().
  
  sync_thread_add_level(): Remove the relaxation of the assertion added in r968.

storage/innobase/btr/btr0btr.c

@@ -1949,7 +1949,12 @@ btr_lift_page_up(
 	mtr_t*		mtr)	/* in: mtr */
 {
 	page_t*		father_page;
+	page_t*		iter_page;
+	page_t*		pages[BTR_MAX_LEVELS];
 	ulint		page_level;
+	ulint		root_page_no;
+	ulint		ancestors;
+	ulint		i;
 
 	ut_ad(btr_page_get_prev(page, mtr) == FIL_NULL);
 	ut_ad(btr_page_get_next(page, mtr) == FIL_NULL);
@@ -1959,6 +1964,30 @@ btr_lift_page_up(
 		btr_page_get_father_node_ptr(index, page, mtr));
 
 	page_level = btr_page_get_level(page, mtr);
+	root_page_no = dict_index_get_page(index);
+
+	ancestors = 1;
+	pages[0] = father_page;
+
+	/* Store all ancestor pages so we can reset their levels later on.
+	We have to do all the searches on the tree now because later on,
+	after we've replaced the first level, the tree is in an inconsistent
+	state and can not be searched. */
+	iter_page = father_page;
+	for (;;) {
+		if (buf_block_get_page_no(buf_block_align(iter_page))
+		    == root_page_no) {
+
+			break;
+		}
+
+		ut_a(ancestors < BTR_MAX_LEVELS);
+
+		iter_page = buf_frame_align(
+			btr_page_get_father_node_ptr(index, iter_page, mtr));
+
+		pages[ancestors++] = iter_page;
+	}
 
 	btr_search_drop_page_hash_index(page);
 
@@ -1970,7 +1999,15 @@ btr_lift_page_up(
 			       index, mtr);
 	lock_update_copy_and_discard(father_page, page);
 
-	btr_page_set_level(father_page, page_level, mtr);
+	/* Go upward to root page, decreasing levels by one. */
+	for (i = 0; i < ancestors; i++) {
+		iter_page = pages[i];
+
+		ut_ad(btr_page_get_level(iter_page, mtr) == (page_level + 1));
+
+		btr_page_set_level(iter_page, page_level, mtr);
+		page_level++;
+	}
 
 	/* Free the file page */
 	btr_page_free(index, page, mtr);

storage/innobase/buf/buf0flu.c

@@ -113,6 +113,7 @@ buf_flush_ready_for_replace(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	if (block->state != BUF_BLOCK_FILE_PAGE) {
 		ut_print_timestamp(stderr);
@@ -148,6 +149,7 @@ buf_flush_ready_for_flush(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&(block->mutex)));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
@@ -559,8 +561,15 @@ buf_flush_try_page(
 
 	ut_a(!block || block->state == BUF_BLOCK_FILE_PAGE);
 
+	if (!block) {
+		mutex_exit(&(buf_pool->mutex));
+		return(0);
+	}
+
+	mutex_enter(&block->mutex);
+
 	if (flush_type == BUF_FLUSH_LIST
-	    && block && buf_flush_ready_for_flush(block, flush_type)) {
+	    && buf_flush_ready_for_flush(block, flush_type)) {
 
 		block->io_fix = BUF_IO_WRITE;
 
@@ -598,6 +607,7 @@ buf_flush_try_page(
 			locked = TRUE;
 		}
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		if (!locked) {
@@ -618,7 +628,7 @@ buf_flush_try_page(
 
 		return(1);
 
-	} else if (flush_type == BUF_FLUSH_LRU && block
+	} else if (flush_type == BUF_FLUSH_LRU
 		   && buf_flush_ready_for_flush(block, flush_type)) {
 
 		/* VERY IMPORTANT:
@@ -659,13 +669,14 @@ buf_flush_try_page(
 		buf_pool mutex: this ensures that the latch is acquired
 		immediately. */
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		buf_flush_write_block_low(block);
 
 		return(1);
 
-	} else if (flush_type == BUF_FLUSH_SINGLE_PAGE && block
+	} else if (flush_type == BUF_FLUSH_SINGLE_PAGE
 		   && buf_flush_ready_for_flush(block, flush_type)) {
 
 		block->io_fix = BUF_IO_WRITE;
@@ -692,6 +703,7 @@ buf_flush_try_page(
 
 		(buf_pool->n_flush[flush_type])++;
 
+		mutex_exit(&block->mutex);
 		mutex_exit(&(buf_pool->mutex));
 
 		rw_lock_s_lock_gen(&(block->lock), BUF_IO_WRITE);
@@ -709,11 +721,12 @@ buf_flush_try_page(
 		buf_flush_write_block_low(block);
 
 		return(1);
-	} else {
-		mutex_exit(&(buf_pool->mutex));
-
-		return(0);
 	}
+
+	mutex_exit(&block->mutex);
+	mutex_exit(&(buf_pool->mutex));
+
+	return(0);
 }
 
 /***************************************************************
@@ -758,34 +771,48 @@ buf_flush_try_neighbors(
 		block = buf_page_hash_get(space, i);
 		ut_a(!block || block->state == BUF_BLOCK_FILE_PAGE);
 
-		if (block && flush_type == BUF_FLUSH_LRU && i != offset
-		    && !block->old) {
+		if (!block) {
+
+			continue;
+
+		} else if (flush_type == BUF_FLUSH_LRU && i != offset
+			   && !block->old) {
 
 			/* We avoid flushing 'non-old' blocks in an LRU flush,
 			because the flushed blocks are soon freed */
 
 			continue;
-		}
+		} else {
 
-		if (block && buf_flush_ready_for_flush(block, flush_type)
-		    && (i == offset || block->buf_fix_count == 0)) {
-			/* We only try to flush those neighbors != offset
-			where the buf fix count is zero, as we then know that
-			we probably can latch the page without a semaphore
-			wait. Semaphore waits are expensive because we must
-			flush the doublewrite buffer before we start
-			waiting. */
+			mutex_enter(&block->mutex);
 
-			mutex_exit(&(buf_pool->mutex));
+			if (buf_flush_ready_for_flush(block, flush_type)
+			    && (i == offset || block->buf_fix_count == 0)) {
+				/* We only try to flush those
+				neighbors != offset where the buf fix count is
+				zero, as we then know that we probably can
+				latch the page without a semaphore wait.
+				Semaphore waits are expensive because we must
+				flush the doublewrite buffer before we start
+				waiting. */
 
-			/* Note: as we release the buf_pool mutex above, in
-			buf_flush_try_page we cannot be sure the page is still
-			in a flushable state: therefore we check it again
-			inside that function. */
+				mutex_exit(&block->mutex);
 
-			count += buf_flush_try_page(space, i, flush_type);
+				mutex_exit(&(buf_pool->mutex));
 
-			mutex_enter(&(buf_pool->mutex));
+				/* Note: as we release the buf_pool mutex
+				above, in buf_flush_try_page we cannot be sure
+				the page is still in a flushable state:
+				therefore we check it again inside that
+				function. */
+
+				count += buf_flush_try_page(space, i,
+							    flush_type);
+
+				mutex_enter(&(buf_pool->mutex));
+			} else {
+				mutex_exit(&block->mutex);
+			}
 		}
 	}
 
@@ -879,12 +906,15 @@ buf_flush_batch(
 		while ((block != NULL) && !found) {
 			ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
+			mutex_enter(&block->mutex);
+
 			if (buf_flush_ready_for_flush(block, flush_type)) {
 
 				found = TRUE;
 				space = block->space;
 				offset = block->offset;
 
+				mutex_exit(&block->mutex);
 				mutex_exit(&(buf_pool->mutex));
 
 				old_page_count = page_count;
@@ -901,10 +931,14 @@ buf_flush_batch(
 
 			} else if (flush_type == BUF_FLUSH_LRU) {
 
+				mutex_exit(&block->mutex);
+
 				block = UT_LIST_GET_PREV(LRU, block);
 			} else {
 				ut_ad(flush_type == BUF_FLUSH_LIST);
 
+				mutex_exit(&block->mutex);
+
 				block = UT_LIST_GET_PREV(flush_list, block);
 			}
 		}
@@ -986,10 +1020,14 @@ buf_flush_LRU_recommendation(void)
 		   + BUF_FLUSH_EXTRA_MARGIN)
 	       && (distance < BUF_LRU_FREE_SEARCH_LEN)) {
 
+		mutex_enter(&block->mutex);
+
 		if (buf_flush_ready_for_replace(block)) {
 			n_replaceable++;
 		}
 
+		mutex_exit(&block->mutex);
+
 		distance++;
 
 		block = UT_LIST_GET_PREV(LRU, block);

storage/innobase/buf/buf0lru.c

@@ -86,6 +86,11 @@ buf_LRU_invalidate_tablespace(
 	block = UT_LIST_GET_LAST(buf_pool->LRU);
 
 	while (block != NULL) {
+		buf_block_t*	prev_block;
+
+		mutex_enter(&block->mutex);
+		prev_block = UT_LIST_GET_PREV(LRU, block);
+
 		ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 
 		if (block->space == id
@@ -112,6 +117,8 @@ buf_LRU_invalidate_tablespace(
 			if (block->is_hashed) {
 				page_no = block->offset;
 
+				mutex_exit(&block->mutex);
+
 				mutex_exit(&(buf_pool->mutex));
 
 				/* Note that the following call will acquire
@@ -138,7 +145,8 @@ buf_LRU_invalidate_tablespace(
 			buf_LRU_block_free_hashed_page(block);
 		}
 next_page:
-		block = UT_LIST_GET_PREV(LRU, block);
+		mutex_exit(&block->mutex);
+		block = prev_block;
 	}
 
 	mutex_exit(&(buf_pool->mutex));
@@ -211,6 +219,9 @@ buf_LRU_search_and_free_block(
 
 	while (block != NULL) {
 		ut_a(block->in_LRU_list);
+
+		mutex_enter(&block->mutex);
+
 		if (buf_flush_ready_for_replace(block)) {
 
 #ifdef UNIV_DEBUG
@@ -226,6 +237,7 @@ buf_LRU_search_and_free_block(
 			buf_LRU_block_remove_hashed_page(block);
 
 			mutex_exit(&(buf_pool->mutex));
+			mutex_exit(&block->mutex);
 
 			/* Remove possible adaptive hash index built on the
 			page; in the case of AWE the block may not have a
@@ -234,15 +246,21 @@ buf_LRU_search_and_free_block(
 			if (block->frame) {
 				btr_search_drop_page_hash_index(block->frame);
 			}
-			mutex_enter(&(buf_pool->mutex));
 
 			ut_a(block->buf_fix_count == 0);
 
+			mutex_enter(&(buf_pool->mutex));
+			mutex_enter(&block->mutex);
+
 			buf_LRU_block_free_hashed_page(block);
 			freed = TRUE;
+			mutex_exit(&block->mutex);
 
 			break;
 		}
+
+		mutex_exit(&block->mutex);
+
 		block = UT_LIST_GET_PREV(LRU, block);
 		distance++;
 
@@ -428,8 +446,12 @@ buf_LRU_get_free_block(void)
 			}
 		}
 
+		mutex_enter(&block->mutex);
+
 		block->state = BUF_BLOCK_READY_FOR_USE;
 
+		mutex_exit(&block->mutex);
+
 		mutex_exit(&(buf_pool->mutex));
 
 		if (started_monitor) {
@@ -838,6 +860,7 @@ buf_LRU_block_free_non_file_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_ad(block);
 
@@ -877,6 +900,7 @@ buf_LRU_block_remove_hashed_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_ad(block);
 
@@ -939,6 +963,7 @@ buf_LRU_block_free_hashed_page(
 {
 #ifdef UNIV_SYNC_DEBUG
 	ut_ad(mutex_own(&(buf_pool->mutex)));
+	ut_ad(mutex_own(&block->mutex));
 #endif /* UNIV_SYNC_DEBUG */
 	ut_a(block->state == BUF_BLOCK_REMOVE_HASH);
 

storage/innobase/dict/dict0crea.c

@@ -700,8 +700,10 @@ dict_truncate_index_tree(
 				/* out: new root page number, or
 				FIL_NULL on failure */
 	dict_table_t*	table,	/* in: the table the index belongs to */
-	rec_t*		rec,	/* in: record in the clustered index of
-				SYS_INDEXES table */
+	btr_pcur_t*	pcur,	/* in/out: persistent cursor pointing to
+				record in the clustered index of
+				SYS_INDEXES table. The cursor may be
+				repositioned in this call. */
 	mtr_t*		mtr)	/* in: mtr having the latch
 				on the record page. The mtr may be
 				committed and restarted in this call. */
@@ -710,6 +712,7 @@ dict_truncate_index_tree(
 	ulint		space;
 	ulint		type;
 	dulint		index_id;
+	rec_t*		rec;
 	byte*		ptr;
 	ulint		len;
 	ulint		comp;
@@ -720,6 +723,7 @@ dict_truncate_index_tree(
 #endif /* UNIV_SYNC_DEBUG */
 
 	ut_a(!dict_table_is_comp(dict_sys->sys_indexes));
+	rec = btr_pcur_get_rec(pcur);
 	ptr = rec_get_nth_field_old(rec, DICT_SYS_INDEXES_PAGE_NO_FIELD, &len);
 
 	ut_ad(len == 4);
@@ -785,10 +789,11 @@ dict_truncate_index_tree(
 	/* We will need to commit the mini-transaction in order to avoid
 	deadlocks in the btr_create() call, because otherwise we would
 	be freeing and allocating pages in the same mini-transaction. */
+	btr_pcur_store_position(pcur, mtr);
 	mtr_commit(mtr);
-	/* mtr_commit() will invalidate rec. */
-	rec = NULL;
+
 	mtr_start(mtr);
+	btr_pcur_restore_position(BTR_MODIFY_LEAF, pcur, mtr);
 
 	/* Find the index corresponding to this SYS_INDEXES record. */
 	for (index = UT_LIST_GET_FIRST(table->indexes);

storage/innobase/fil/fil0fil.c

@@ -4416,29 +4416,47 @@ fil_flush_file_spaces(
 {
 	fil_system_t*	system	= fil_system;
 	fil_space_t*	space;
+	ulint*		space_ids;
+	ulint		n_space_ids;
+	ulint		i;
 
 	mutex_enter(&(system->mutex));
 
-	space = UT_LIST_GET_FIRST(system->unflushed_spaces);
+	n_space_ids = UT_LIST_GET_LEN(system->unflushed_spaces);
+	if (n_space_ids == 0) {
 
-	while (space) {
-		if (space->purpose == purpose && !space->is_being_deleted) {
+		mutex_exit(&system->mutex);
+		return;
+	}
 
-			space->n_pending_flushes++; /* prevent dropping of
-						    the space while we are
-						    flushing */
-			mutex_exit(&(system->mutex));
+	/* Assemble a list of space ids to flush.  Previously, we
+	traversed system->unflushed_spaces and called UT_LIST_GET_NEXT()
+	on a space that was just removed from the list by fil_flush().
+	Thus, the space could be dropped and the memory overwritten. */
+	space_ids = mem_alloc(n_space_ids * sizeof *space_ids);
 
-			fil_flush(space->id);
+	n_space_ids = 0;
 
-			mutex_enter(&(system->mutex));
+	for (space = UT_LIST_GET_FIRST(system->unflushed_spaces);
+	     space;
+	     space = UT_LIST_GET_NEXT(unflushed_spaces, space)) {
 
-			space->n_pending_flushes--;
+		if (space->purpose == purpose && !space->is_being_deleted) {
+
+			space_ids[n_space_ids++] = space->id;
 		}
-		space = UT_LIST_GET_NEXT(unflushed_spaces, space);
 	}
 
-	mutex_exit(&(system->mutex));
+	mutex_exit(&system->mutex);
+
+	/* Flush the spaces.  It will not hurt to call fil_flush() on
+	a non-existing space id. */
+	for (i = 0; i < n_space_ids; i++) {
+
+		fil_flush(space_ids[i]);
+	}
+
+	mem_free(space_ids);
 }
 
 /**********************************************************************

storage/innobase/include/btr0btr.h

@@ -23,7 +23,17 @@ special big record storage structure */
 
 #define	BTR_PAGE_MAX_REC_SIZE	(UNIV_PAGE_SIZE / 2 - 200)
 
-/* Latching modes for the search function (in btr0cur.*) */
+/* Maximum depth of a B-tree in InnoDB. Note that this isn't a maximum as
+such; none of the tree operations avoid producing trees bigger than this. It
+is instead a "max depth that other code must work with", useful for e.g.
+fixed-size arrays that must store some information about each level in a
+tree. In other words: if a B-tree with bigger depth than this is
+encountered, it is not acceptable for it to lead to mysterious memory
+corruption, but it is acceptable for the program to die with a clear assert
+failure. */
+#define BTR_MAX_LEVELS		100
+
+/* Latching modes for btr_cur_search_to_nth_level(). */
 #define BTR_SEARCH_LEAF		RW_S_LATCH
 #define BTR_MODIFY_LEAF		RW_X_LATCH
 #define BTR_NO_LATCHES		RW_NO_LATCH

storage/innobase/include/buf0buf.h

@@ -461,8 +461,8 @@ Gets the mutex number protecting the page record lock hash chain in the lock
 table. */
 UNIV_INLINE
 mutex_t*
-buf_frame_get_lock_mutex(
-/*=====================*/
+buf_frame_get_mutex(
+/*================*/
 			/* out: mutex */
 	byte*	ptr);	/* in: pointer to within a buffer frame */
 /***********************************************************************
@@ -713,7 +713,10 @@ struct buf_block_struct{
 
 	ulint		magic_n;	/* magic number to check */
 	ulint		state;		/* state of the control block:
-					BUF_BLOCK_NOT_USED, ... */
+					BUF_BLOCK_NOT_USED, ...; changing
+					this is only allowed when a thread
+					has BOTH the buffer pool mutex AND
+					block->mutex locked */
 	byte*		frame;		/* pointer to buffer frame which
 					is of size UNIV_PAGE_SIZE, and
 					aligned to an address divisible by
@@ -731,8 +734,12 @@ struct buf_block_struct{
 	ulint		offset;		/* page number within the space */
 	ulint		lock_hash_val;	/* hashed value of the page address
 					in the record lock hash table */
-	mutex_t*	lock_mutex;	/* mutex protecting the chain in the
-					record lock hash table */
+	mutex_t		mutex;		/* mutex protecting this block:
+					state (also protected by the buffer
+					pool mutex), io_fix, buf_fix_count,
+					and accessed; we introduce this new
+					mutex in InnoDB-5.1 to relieve
+					contention on the buffer pool mutex */
 	rw_lock_t	lock;		/* read-write lock of the buffer
 					frame */
 	buf_block_t*	hash;		/* node used in chaining to the page
@@ -788,20 +795,27 @@ struct buf_block_struct{
 					in heuristic algorithms, because of
 					the possibility of a wrap-around! */
 	ulint		freed_page_clock;/* the value of freed_page_clock
-					buffer pool when this block was
-					last time put to the head of the
-					LRU list */
+					of the buffer pool when this block was
+					the last time put to the head of the
+					LRU list; a thread is allowed to
+					read this for heuristic purposes
+					without holding any mutex or latch */
 	ibool		old;		/* TRUE if the block is in the old
 					blocks in the LRU list */
 	ibool		accessed;	/* TRUE if the page has been accessed
 					while in the buffer pool: read-ahead
 					may read in pages which have not been
-					accessed yet */
+					accessed yet; this is protected by
+					block->mutex; a thread is allowed to
+					read this for heuristic purposes
+					without holding any mutex or latch */
 	ulint		buf_fix_count;	/* count of how manyfold this block
-					is currently bufferfixed */
+					is currently bufferfixed; this is
+					protected by block->mutex */
 	ulint		io_fix;		/* if a read is pending to the frame,
 					io_fix is BUF_IO_READ, in the case
-					of a write BUF_IO_WRITE, otherwise 0 */
+					of a write BUF_IO_WRITE, otherwise 0;
+					this is protected by block->mutex */
 	/* 4. Optimistic search field */
 
 	dulint		modify_clock;	/* this clock is incremented every
@@ -959,7 +973,9 @@ struct buf_pool_struct{
 					number of buffer blocks removed from
 					the end of the LRU list; NOTE that
 					this counter may wrap around at 4
-					billion! */
+					billion! A thread is allowed to
+					read this for heuristic purposes
+					without holding any mutex or latch */
 	ulint		LRU_flush_ended;/* when an LRU flush ends for a page,
 					this is incremented by one; this is
 					set to zero when a buffer block is

storage/innobase/include/buf0buf.ic

@@ -337,8 +337,8 @@ Gets the mutex number protecting the page record lock hash chain in the lock
 table. */
 UNIV_INLINE
 mutex_t*
-buf_frame_get_lock_mutex(
-/*=====================*/
+buf_frame_get_mutex(
+/*================*/
 			/* out: mutex */
 	byte*	ptr)	/* in: pointer to within a buffer frame */
 {
@@ -346,7 +346,7 @@ buf_frame_get_lock_mutex(
 
 	block = buf_block_align(ptr);
 
-	return(block->lock_mutex);
+	return(&block->mutex);
 }
 
 /*************************************************************************
@@ -519,6 +519,7 @@ buf_block_buf_fix_inc_debug(
 	ret = rw_lock_s_lock_func_nowait(&(block->debug_latch), file, line);
 
 	ut_ad(ret == TRUE);
+	ut_ad(mutex_own(&block->mutex));
 #endif
 	block->buf_fix_count++;
 }
@@ -531,6 +532,9 @@ buf_block_buf_fix_inc(
 /*==================*/
 	buf_block_t*	block)	/* in: block to bufferfix */
 {
+#ifdef UNIV_SYNC_DEBUG
+	ut_ad(mutex_own(&block->mutex));
+#endif
 	block->buf_fix_count++;
 }
 #endif /* UNIV_SYNC_DEBUG */
@@ -625,23 +629,24 @@ buf_page_release(
 
 	ut_ad(block);
 
-	mutex_enter_fast(&(buf_pool->mutex));
-
 	ut_a(block->state == BUF_BLOCK_FILE_PAGE);
 	ut_a(block->buf_fix_count > 0);
 
 	if (rw_latch == RW_X_LATCH && mtr->modifications) {
-
+		mutex_enter(&buf_pool->mutex);
 		buf_flush_note_modification(block, mtr);
+		mutex_exit(&buf_pool->mutex);
 	}
 
+	mutex_enter(&block->mutex);
+
 #ifdef UNIV_SYNC_DEBUG
 	rw_lock_s_unlock(&(block->debug_latch));
 #endif
 	buf_fix_count = block->buf_fix_count;
 	block->buf_fix_count = buf_fix_count - 1;
 
-	mutex_exit(&(buf_pool->mutex));
+	mutex_exit(&block->mutex);
 
 	if (rw_latch == RW_S_LATCH) {
 		rw_lock_s_unlock(&(block->lock));

storage/innobase/include/dict0crea.h

@@ -62,8 +62,10 @@ dict_truncate_index_tree(
 				/* out: new root page number, or
 				FIL_NULL on failure */
 	dict_table_t*	table,	/* in: the table the index belongs to */
-	rec_t*		rec,	/* in: record in the clustered index of
-				SYS_INDEXES table */
+	btr_pcur_t*	pcur,	/* in/out: persistent cursor pointing to
+				record in the clustered index of
+				SYS_INDEXES table. The cursor may be
+				repositioned in this call. */
 	mtr_t*		mtr);	/* in: mtr having the latch
 				on the record page. The mtr may be
 				committed and restarted in this call. */

storage/innobase/include/ut0lst.h

@@ -123,27 +123,36 @@ name, NODE1 and NODE2 are pointers to nodes. */
 	}\
 }\
 
+/* Invalidate the pointers in a list node. */
+#ifdef UNIV_DEBUG
+# define UT_LIST_REMOVE_CLEAR(NAME, N)		\
+((N)->NAME.prev = (N)->NAME.next = (void*) -1)
+#else
+# define UT_LIST_REMOVE_CLEAR(NAME, N) while (0)
+#endif
+
 /***********************************************************************
 Removes a node from a two-way linked list. BASE has to be the base node
 (not a pointer to it). N has to be the pointer to the node to be removed
 from the list. NAME is the list name. */
 
-#define UT_LIST_REMOVE(NAME, BASE, N)\
-{\
-	ut_ad(N);\
-	ut_a((BASE).count > 0);\
-	((BASE).count)--;\
-	if (((N)->NAME).next != NULL) {\
-		((((N)->NAME).next)->NAME).prev = ((N)->NAME).prev;\
-	} else {\
-		(BASE).end = ((N)->NAME).prev;\
-	}\
-	if (((N)->NAME).prev != NULL) {\
-		((((N)->NAME).prev)->NAME).next = ((N)->NAME).next;\
-	} else {\
-		(BASE).start = ((N)->NAME).next;\
-	}\
-}\
+#define UT_LIST_REMOVE(NAME, BASE, N)					\
+do {									\
+	ut_ad(N);							\
+	ut_a((BASE).count > 0);						\
+	((BASE).count)--;						\
+	if (((N)->NAME).next != NULL) {					\
+		((((N)->NAME).next)->NAME).prev = ((N)->NAME).prev;	\
+	} else {							\
+		(BASE).end = ((N)->NAME).prev;				\
+	}								\
+	if (((N)->NAME).prev != NULL) {					\
+		((((N)->NAME).prev)->NAME).next = ((N)->NAME).next;	\
+	} else {							\
+		(BASE).start = ((N)->NAME).next;			\
+	}								\
+	UT_LIST_REMOVE_CLEAR(NAME, N);					\
+} while (0)
 
 /************************************************************************
 Gets the next node in a two-way list. NAME is the name of the list

storage/innobase/row/row0mysql.c

@@ -2820,12 +2820,10 @@ row_truncate_table_for_mysql(
 			goto next_rec;
 		}
 
-		btr_pcur_store_position(&pcur, &mtr);
+		/* This call may commit and restart mtr
+		and reposition pcur. */
+		root_page_no = dict_truncate_index_tree(table, &pcur, &mtr);
 
-		/* This call may commit and restart mtr. */
-		root_page_no = dict_truncate_index_tree(table, rec, &mtr);
-
-		btr_pcur_restore_position(BTR_MODIFY_LEAF, &pcur, &mtr);
 		rec = btr_pcur_get_rec(&pcur);
 
 		if (root_page_no != FIL_NULL) {