Merge pull request #245 from sensssz/10.1-vats

MDEV-11039 - Add new scheduling algorithm for reducing tail latencies

storage/innobase/handler/ha_innodb.cc

@@ -300,6 +300,22 @@ static TYPELIB innodb_checksum_algorithm_typelib = {
 	NULL
 };
 
+/** Possible values of the parameter innodb_lock_schedule_algorithm */
+static const char* innodb_lock_schedule_algorithm_names[] = {
+	"fcfs",
+	"vats",
+	NullS
+};
+
+/** Used to define an enumerate type of the system variable
+innodb_lock_schedule_algorithm. */
+static TYPELIB innodb_lock_schedule_algorithm_typelib = {
+	array_elements(innodb_lock_schedule_algorithm_names) - 1,
+	"innodb_lock_schedule_algorithm_typelib",
+	innodb_lock_schedule_algorithm_names,
+	NULL
+};
+
 /* The following counter is used to convey information to InnoDB
 about server activity: in case of normal DML ops it is not
 sensible to call srv_active_wake_master_thread after each
@@ -19013,6 +19029,18 @@ static MYSQL_SYSVAR_ULONG(doublewrite_batch_size, srv_doublewrite_batch_size,
   NULL, NULL, 120, 1, 127, 0);
 #endif /* defined UNIV_DEBUG || defined UNIV_PERF_DEBUG */
 
+static MYSQL_SYSVAR_ENUM(lock_schedule_algorithm, innodb_lock_schedule_algorithm,
+  PLUGIN_VAR_RQCMDARG,
+  "The algorithm Innodb uses for deciding which locks to grant next when"
+  " a lock is released. Possible values are"
+  " FCFS"
+    " grant the locks in First-Come-First-Served order;"
+  " VATS"
+    " use the Variance-Aware-Transaction-Scheduling algorithm, which"
+    " uses an Eldest-Transaction-First heuristic.",
+  NULL, NULL, INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS,
+  &innodb_lock_schedule_algorithm_typelib);
+
 static MYSQL_SYSVAR_LONG(buffer_pool_instances, innobase_buffer_pool_instances,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "Number of buffer pool instances, set to higher value on high-end machines to increase scalability",
@@ -19828,6 +19856,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(ft_sort_pll_degree),
   MYSQL_SYSVAR(large_prefix),
   MYSQL_SYSVAR(force_load_corrupted),
+  MYSQL_SYSVAR(lock_schedule_algorithm),
   MYSQL_SYSVAR(locks_unsafe_for_binlog),
   MYSQL_SYSVAR(lock_wait_timeout),
 #ifdef UNIV_LOG_ARCHIVE

storage/innobase/include/lock0lock.h

@@ -43,6 +43,15 @@ Created 5/7/1996 Heikki Tuuri
 extern ibool	lock_print_waits;
 #endif /* UNIV_DEBUG */
 
+/** Alternatives for innodb_lock_schedule_algorithm, which can be changed by
+    setting innodb_lock_schedule_algorithm. */
+enum innodb_lock_schedule_algorithm_t {
+    INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS,		/*!< First Come First Served */
+    INNODB_LOCK_SCHEDULE_ALGORITHM_VATS         /*!< Variance-Aware-Transaction-Scheduling */
+};
+
+extern ulong innodb_lock_schedule_algorithm;
+
 /*********************************************************************//**
 Gets the size of a lock struct.
 @return	size in bytes */

storage/innobase/lock/lock0lock.cc

@@ -76,6 +76,9 @@ bitmap */
 
 #define LOCK_PAGE_BITMAP_MARGIN		64
 
+/** Lock scheduling algorithm */
+ulong innodb_lock_schedule_algorithm = INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS;
+
 /* An explicit record lock affects both the record and the gap before it.
 An implicit x-lock does not affect the gap, it only locks the index
 record from read or update.
@@ -385,6 +388,9 @@ extern "C" int thd_need_wait_for(const MYSQL_THD thd);
 extern "C"
 int thd_need_ordering_with(const MYSQL_THD thd, const MYSQL_THD other_thd);
 
+extern "C"
+int thd_deadlock_victim_preference(const MYSQL_THD thd1, const MYSQL_THD thd2);
+
 /** Stack to use during DFS search. Currently only a single stack is required
 because there is no parallel deadlock check. This stack is protected by
 the lock_sys_t::mutex. */
@@ -1982,6 +1988,84 @@ wsrep_print_wait_locks(
 }
 #endif /* WITH_WSREP */
 
+/*********************************************************************//**
+Check if lock1 has higher priority than lock2.
+NULL has lowest priority.
+Respect the preference of the upper server layer to reduce conflict
+during in-order parallel replication.
+If neither of them is wait lock, the first one has higher priority.
+If only one of them is a wait lock, it has lower priority.
+Otherwise, the one with an older transaction has higher priority.
+@returns true if lock1 has higher priority, false otherwise. */
+bool
+has_higher_priority(
+	lock_t *lock1,
+	lock_t *lock2)
+{
+	if (lock1 == NULL) {
+		return false;
+	} else if (lock2 == NULL) {
+		return true;
+	}
+	// Ask the upper server layer if any of the two trx should be prefered.
+	int preference = thd_deadlock_victim_preference(lock1->trx->mysql_thd, lock2->trx->mysql_thd);
+	if (preference == -1) {
+		// lock1 is preferred as a victim, so lock2 has higher priority
+		return false;
+	} else if (preference == 1) {
+		// lock2 is preferred as a victim, so lock1 has higher priority
+		return true;
+	}
+	// No preference. Compre them by wait mode and trx age.
+	if (!lock_get_wait(lock1)) {
+		return true;
+	} else if (!lock_get_wait(lock2)) {
+		return false;
+	}
+	return lock1->trx->start_time < lock2->trx->start_time;
+}
+
+/*********************************************************************//**
+Insert a lock to the hash list according to the mode (whether it is a wait lock)
+and the age of the transaction the it is associated with.
+If the lock is not a wait lock, insert it to the head of the hash list.
+Otherwise, insert it to the middle of the wait locks according to the age of the
+transaciton.
+*/
+static
+void
+lock_rec_insert_by_trx_age(
+	lock_t *in_lock, /*!< in: lock to be insert */
+	bool wait)		 	/*!< in: whether it's a wait lock */
+{
+	ulint					space;
+	ulint					page_no;
+	ulint					rec_fold;
+	hash_cell_t*	cell;
+	lock_t*				node;
+	lock_t*				next;
+
+	space = in_lock->un_member.rec_lock.space;
+	page_no = in_lock->un_member.rec_lock.page_no;
+	rec_fold = lock_rec_fold(space, page_no);
+	cell = hash_get_nth_cell(lock_sys->rec_hash,
+					hash_calc_hash(rec_fold, lock_sys->rec_hash));
+
+	node = (lock_t *) cell->node;
+	// If in_lock is not a wait lock, we insert it to the head of the list.
+	if (node == NULL || !wait || has_higher_priority(in_lock, node)) {
+		cell->node = in_lock;
+		in_lock->hash = node;
+		return;
+	}
+	while (node != NULL && has_higher_priority((lock_t *) node->hash, in_lock)) {
+		node = (lock_t *) node->hash;
+	}
+	next = (lock_t *) node->hash;
+	node->hash = in_lock;
+	in_lock->hash = next;
+}
+
 /*********************************************************************//**
 Creates a new record lock and inserts it to the lock queue. Does NOT check
 for deadlocks or lock compatibility!
@@ -2146,11 +2230,11 @@ lock_rec_create(
 		trx_mutex_exit(c_lock->trx);
 	} else {
 		HASH_INSERT(lock_t, hash, lock_sys->rec_hash,
-			    lock_rec_fold(space, page_no), lock);
+					lock_rec_fold(space, page_no), lock);
 	}
 #else
 	HASH_INSERT(lock_t, hash, lock_sys->rec_hash,
-		    lock_rec_fold(space, page_no), lock);
+				lock_rec_fold(space, page_no), lock);
 #endif /* WITH_WSREP */
 
 	if (!caller_owns_trx_mutex) {
@@ -2281,6 +2365,13 @@ lock_rec_enqueue_waiting(
 		return(DB_SUCCESS_LOCKED_REC);
 	}
 
+    // Move it only when it does not cause a deadlock.
+    if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS) {
+        HASH_DELETE(lock_t, hash, lock_sys->rec_hash,
+                    lock_rec_fold(buf_block_get_space(block), buf_block_get_page_no(block)), lock);
+        lock_rec_insert_by_trx_age(lock, true);
+    }
+
 	trx->lock.que_state = TRX_QUE_LOCK_WAIT;
 
 	trx->lock.was_chosen_as_deadlock_victim = FALSE;
@@ -2822,6 +2913,27 @@ lock_rec_cancel(
 	trx_mutex_exit(lock->trx);
 }
 
+/*************************************************************//**
+Move the lock to the head of the hash list. */
+static
+void
+lock_rec_move_to_front(
+	lock_t *lock_to_move,	/*!< in: lock to be moved */
+	ulint rec_fold)			 /*!< in: rec fold of the lock */
+{
+	if (lock_to_move != NULL)
+	{
+		// Move the target lock to the head of the list
+		hash_cell_t* cell = hash_get_nth_cell(lock_sys->rec_hash,
+													hash_calc_hash(rec_fold, lock_sys->rec_hash));
+		if (lock_to_move != cell->node) {
+			lock_t *next = (lock_t *) cell->node;
+			cell->node = lock_to_move;
+			lock_to_move->hash = next;
+		}
+	}
+}
+
 /*************************************************************//**
 Removes a record lock request, waiting or granted, from the queue and
 grants locks to other transactions in the queue if they now are entitled
@@ -2839,7 +2951,9 @@ lock_rec_dequeue_from_page(
 {
 	ulint		space;
 	ulint		page_no;
+	ulint 	rec_fold;
 	lock_t*		lock;
+	lock_t*		previous = NULL;
 	trx_lock_t*	trx_lock;
 
 	ut_ad(lock_mutex_own());
@@ -2850,6 +2964,7 @@ lock_rec_dequeue_from_page(
 
 	space = in_lock->un_member.rec_lock.space;
 	page_no = in_lock->un_member.rec_lock.page_no;
+	rec_fold = lock_rec_fold(space, page_no);
 
 	in_lock->index->table->n_rec_locks--;
 
@@ -2861,20 +2976,51 @@ lock_rec_dequeue_from_page(
 	MONITOR_INC(MONITOR_RECLOCK_REMOVED);
 	MONITOR_DEC(MONITOR_NUM_RECLOCK);
 
-	/* Check if waiting locks in the queue can now be granted: grant
-	locks if there are no conflicting locks ahead. Stop at the first
-	X lock that is waiting or has been granted. */
+	if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS) {
+		/* Check if waiting locks in the queue can now be granted: grant
+		locks if there are no conflicting locks ahead. Stop at the first
+		X lock that is waiting or has been granted. */
 
-	for (lock = lock_rec_get_first_on_page_addr(space, page_no);
-	     lock != NULL;
-	     lock = lock_rec_get_next_on_page(lock)) {
+		for (lock = lock_rec_get_first_on_page_addr(space, page_no);
+		     lock != NULL;
+		     lock = lock_rec_get_next_on_page(lock)) {
 
-		if (lock_get_wait(lock)
-		    && !lock_rec_has_to_wait_in_queue(lock)) {
+			if (lock_get_wait(lock)
+			    && !lock_rec_has_to_wait_in_queue(lock)) {
 
-			/* Grant the lock */
-			ut_ad(lock->trx != in_lock->trx);
-			lock_grant(lock);
+				/* Grant the lock */
+				ut_ad(lock->trx != in_lock->trx);
+				lock_grant(lock);
+			}
+		}
+	} else {
+		/* Grant locks if there are no conflicting locks ahead.
+		   Move granted locks to the head of the list. */
+		for (lock = lock_rec_get_first_on_page_addr(space, page_no);
+				 lock != NULL;) {
+
+			/* If the lock is a wait lock on this page, and it does not need to wait. */
+			if ((lock->un_member.rec_lock.space == space)
+					&& (lock->un_member.rec_lock.page_no == page_no)
+					&& lock_get_wait(lock)
+					&& !lock_rec_has_to_wait_in_queue(lock)) {
+
+				lock_grant(lock);
+
+				if (previous != NULL) {
+					/* Move the lock to the head of the list. */
+					HASH_GET_NEXT(hash, previous) = HASH_GET_NEXT(hash, lock);
+					lock_rec_move_to_front(lock, rec_fold);
+				} else {
+					/* Already at the head of the list. */
+					previous = lock;
+				}
+				/* Move on to the next lock. */
+				lock = static_cast<lock_t *>(HASH_GET_NEXT(hash, previous));
+			} else {
+				previous = lock;
+				lock = static_cast<lock_t *>(HASH_GET_NEXT(hash, lock));
+			}
 		}
 	}
 }
@@ -4080,7 +4226,8 @@ lock_get_first_lock(
 	}
 
 	ut_a(lock != NULL);
-	ut_a(lock != ctx->wait_lock);
+	ut_a(lock != ctx->wait_lock ||
+            innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS);
 	ut_ad(lock_get_type_low(lock) == lock_get_type_low(ctx->wait_lock));
 
 	return(lock);
@@ -6287,8 +6434,10 @@ lock_rec_queue_validate(
 				mode, 0, 0, block, heap_no, lock->trx));
 #endif /* WITH_WSREP */
 
-		} else if (lock_get_wait(lock) && !lock_rec_get_gap(lock)) {
-
+		} else if (lock_get_wait(lock) && !lock_rec_get_gap(lock)
+				   && innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS) {
+			// If using VATS, it's possible that a wait lock is inserted to a place in the list
+			// such that it does not need to wait.
 			ut_a(lock_rec_has_to_wait_in_queue(lock));
 		}
 	}

storage/xtradb/handler/ha_innodb.cc

@@ -348,6 +348,23 @@ static TYPELIB innodb_empty_free_list_algorithm_typelib = {
 	NULL
 };
 
+/** Possible values of the parameter innodb_lock_schedule_algorithm */
+static const char* innodb_lock_schedule_algorithm_names[] = {
+	"fcfs",
+	"vats",
+	NullS
+};
+
+/** Used to define an enumerate type of the system variable
+innodb_lock_schedule_algorithm. */
+static TYPELIB innodb_lock_schedule_algorithm_typelib = {
+	array_elements(innodb_lock_schedule_algorithm_names) - 1,
+	"innodb_lock_schedule_algorithm_typelib",
+	innodb_lock_schedule_algorithm_names,
+	NULL
+};
+
+
 /* The following counter is used to convey information to InnoDB
 about server activity: in case of normal DML ops it is not
 sensible to call srv_active_wake_master_thread after each
@@ -20473,6 +20490,18 @@ static MYSQL_SYSVAR_ENUM(empty_free_list_algorithm,
   innodb_srv_empty_free_list_algorithm_validate, NULL, SRV_EMPTY_FREE_LIST_BACKOFF,
   &innodb_empty_free_list_algorithm_typelib);
 
+static MYSQL_SYSVAR_ENUM(lock_schedule_algorithm, innodb_lock_schedule_algorithm,
+  PLUGIN_VAR_RQCMDARG,
+  "The algorithm Innodb uses for deciding which locks to grant next when"
+  " a lock is released. Possible values are"
+  " FCFS"
+    " grant the locks in First-Come-First-Served order;"
+  " VATS"
+    " use the Variance-Aware-Transaction-Scheduling algorithm, which"
+    " uses an Eldest-Transaction-First heuristic.",
+  NULL, NULL, INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS,
+  &innodb_lock_schedule_algorithm_typelib);
+
 static MYSQL_SYSVAR_LONG(buffer_pool_instances, innobase_buffer_pool_instances,
   PLUGIN_VAR_RQCMDARG | PLUGIN_VAR_READONLY,
   "Number of buffer pool instances, set to higher value on high-end machines to increase scalability",
@@ -21366,6 +21395,7 @@ static struct st_mysql_sys_var* innobase_system_variables[]= {
   MYSQL_SYSVAR(ft_sort_pll_degree),
   MYSQL_SYSVAR(large_prefix),
   MYSQL_SYSVAR(force_load_corrupted),
+  MYSQL_SYSVAR(lock_schedule_algorithm),
   MYSQL_SYSVAR(locks_unsafe_for_binlog),
   MYSQL_SYSVAR(lock_wait_timeout),
 #ifdef UNIV_LOG_ARCHIVE

storage/xtradb/include/lock0lock.h

@@ -45,6 +45,15 @@ Created 5/7/1996 Heikki Tuuri
 extern ibool	lock_print_waits;
 #endif /* UNIV_DEBUG */
 
+/** Alternatives for innodb_lock_schedule_algorithm, which can be changed by
+    setting innodb_lock_schedule_algorithm. */
+enum innodb_lock_schedule_algorithm_t {
+    INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS,		/*!< First Come First Served */
+    INNODB_LOCK_SCHEDULE_ALGORITHM_VATS         /*!< Variance-Aware-Transaction-Scheduling */
+};
+
+extern ulong innodb_lock_schedule_algorithm;
+
 extern ulint	srv_n_lock_deadlock_count;
 
 /*********************************************************************//**

storage/xtradb/lock/lock0lock.cc

@@ -76,6 +76,9 @@ bitmap */
 
 #define LOCK_PAGE_BITMAP_MARGIN		64
 
+/** Lock scheduling algorithm */
+ulong innodb_lock_schedule_algorithm = INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS;
+
 /* An explicit record lock affects both the record and the gap before it.
 An implicit x-lock does not affect the gap, it only locks the index
 record from read or update.
@@ -385,6 +388,9 @@ extern "C" int thd_need_wait_for(const MYSQL_THD thd);
 extern "C"
 int thd_need_ordering_with(const MYSQL_THD thd, const MYSQL_THD other_thd);
 
+extern "C"
+int thd_deadlock_victim_preference(const MYSQL_THD thd1, const MYSQL_THD thd2);
+
 /** Stack to use during DFS search. Currently only a single stack is required
 because there is no parallel deadlock check. This stack is protected by
 the lock_sys_t::mutex. */
@@ -2005,6 +2011,84 @@ wsrep_print_wait_locks(
 }
 #endif /* WITH_WSREP */
 
+/*********************************************************************//**
+Check if lock1 has higher priority than lock2.
+NULL has lowest priority.
+Respect the preference of the upper server layer to reduce conflict
+during in-order parallel replication.
+If neither of them is wait lock, the first one has higher priority.
+If only one of them is a wait lock, it has lower priority.
+Otherwise, the one with an older transaction has higher priority.
+@returns true if lock1 has higher priority, false otherwise. */
+bool
+has_higher_priority(
+	lock_t *lock1,
+	lock_t *lock2)
+{
+	if (lock1 == NULL) {
+		return false;
+	} else if (lock2 == NULL) {
+		return true;
+	}
+	// Ask the upper server layer if any of the two trx should be prefered.
+	int preference = thd_deadlock_victim_preference(lock1->trx->mysql_thd, lock2->trx->mysql_thd);
+	if (preference == -1) {
+		// lock1 is preferred as a victim, so lock2 has higher priority
+		return false;
+	} else if (preference == 1) {
+		// lock2 is preferred as a victim, so lock1 has higher priority
+		return true;
+	}
+	// No preference. Compre them by wait mode and trx age.
+	if (!lock_get_wait(lock1)) {
+		return true;
+	} else if (!lock_get_wait(lock2)) {
+		return false;
+	}
+	return lock1->trx->start_time < lock2->trx->start_time;
+}
+
+/*********************************************************************//**
+Insert a lock to the hash list according to the mode (whether it is a wait lock)
+and the age of the transaction the it is associated with.
+If the lock is not a wait lock, insert it to the head of the hash list.
+Otherwise, insert it to the middle of the wait locks according to the age of the
+transaciton.
+*/
+static
+void
+lock_rec_insert_by_trx_age(
+	lock_t *in_lock, /*!< in: lock to be insert */
+	bool wait)		 	/*!< in: whether it's a wait lock */
+{
+	ulint					space;
+	ulint					page_no;
+	ulint 				rec_fold;
+	hash_cell_t*		cell;
+	lock_t*				node;
+	lock_t*				next;
+
+	space = in_lock->un_member.rec_lock.space;
+	page_no = in_lock->un_member.rec_lock.page_no;
+	rec_fold = lock_rec_fold(space, page_no);
+	cell = hash_get_nth_cell(lock_sys->rec_hash,
+					hash_calc_hash(rec_fold, lock_sys->rec_hash));
+
+	node = (lock_t *) cell->node;
+	// If in_lock is not a wait lock, we insert it to the head of the list.
+	if (node == NULL || !wait || has_higher_priority(in_lock, node)) {
+		cell->node = in_lock;
+		in_lock->hash = node;
+		return;
+	}
+	while (node != NULL && has_higher_priority((lock_t *) node->hash, in_lock)) {
+		node = (lock_t *) node->hash;
+	}
+	next = (lock_t *) node->hash;
+	node->hash = in_lock;
+	in_lock->hash = next;
+}
+
 /*********************************************************************//**
 Creates a new record lock and inserts it to the lock queue. Does NOT check
 for deadlocks or lock compatibility!
@@ -2169,11 +2253,11 @@ lock_rec_create(
 		trx_mutex_exit(c_lock->trx);
 	} else {
 		HASH_INSERT(lock_t, hash, lock_sys->rec_hash,
-			    lock_rec_fold(space, page_no), lock);
+					lock_rec_fold(space, page_no), lock);
 	}
 #else
 	HASH_INSERT(lock_t, hash, lock_sys->rec_hash,
-		    lock_rec_fold(space, page_no), lock);
+				lock_rec_fold(space, page_no), lock);
 #endif /* WITH_WSREP */
 
 	lock_sys->rec_num++;
@@ -2309,6 +2393,13 @@ lock_rec_enqueue_waiting(
 		return(DB_SUCCESS_LOCKED_REC);
 	}
 
+    // Move it only when it does not cause a deadlock.
+    if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS) {
+        HASH_DELETE(lock_t, hash, lock_sys->rec_hash,
+                    lock_rec_fold(buf_block_get_space(block), buf_block_get_page_no(block)), lock);
+        lock_rec_insert_by_trx_age(lock, true);
+    }
+
 	trx->lock.que_state = TRX_QUE_LOCK_WAIT;
 
 	trx->lock.was_chosen_as_deadlock_victim = FALSE;
@@ -2858,6 +2949,27 @@ lock_rec_cancel(
 	trx_mutex_exit(lock->trx);
 }
 
+/*************************************************************//**
+Move the lock to the head of the hash list. */
+static
+void
+lock_rec_move_to_front(
+	lock_t *lock_to_move,	/*!< in: lock to be moved */
+	ulint rec_fold)			 /*!< in: rec fold of the lock */
+{
+	if (lock_to_move != NULL)
+	{
+		// Move the target lock to the head of the list
+		hash_cell_t* cell = hash_get_nth_cell(lock_sys->rec_hash,
+        	                  hash_calc_hash(rec_fold, lock_sys->rec_hash));
+		if (lock_to_move != cell->node) {
+			lock_t *next = (lock_t *) cell->node;
+			cell->node = lock_to_move;
+			lock_to_move->hash = next;
+		}
+	}
+}
+
 /*************************************************************//**
 Removes a record lock request, waiting or granted, from the queue and
 grants locks to other transactions in the queue if they now are entitled
@@ -2875,7 +2987,9 @@ lock_rec_dequeue_from_page(
 {
 	ulint		space;
 	ulint		page_no;
+	ulint 		rec_fold;
 	lock_t*		lock;
+	lock_t*		previous = NULL;
 	trx_lock_t*	trx_lock;
 
 	ut_ad(lock_mutex_own());
@@ -2886,6 +3000,7 @@ lock_rec_dequeue_from_page(
 
 	space = in_lock->un_member.rec_lock.space;
 	page_no = in_lock->un_member.rec_lock.page_no;
+	rec_fold = lock_rec_fold(space, page_no);
 
 	in_lock->index->table->n_rec_locks--;
 
@@ -2898,20 +3013,51 @@ lock_rec_dequeue_from_page(
 	MONITOR_INC(MONITOR_RECLOCK_REMOVED);
 	MONITOR_DEC(MONITOR_NUM_RECLOCK);
 
-	/* Check if waiting locks in the queue can now be granted: grant
-	locks if there are no conflicting locks ahead. Stop at the first
-	X lock that is waiting or has been granted. */
+	if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS) {
+		/* Check if waiting locks in the queue can now be granted: grant
+		locks if there are no conflicting locks ahead. Stop at the first
+		X lock that is waiting or has been granted. */
 
-	for (lock = lock_rec_get_first_on_page_addr(space, page_no);
-	     lock != NULL;
-	     lock = lock_rec_get_next_on_page(lock)) {
+		for (lock = lock_rec_get_first_on_page_addr(space, page_no);
+		     lock != NULL;
+		     lock = lock_rec_get_next_on_page(lock)) {
 
-		if (lock_get_wait(lock)
-		    && !lock_rec_has_to_wait_in_queue(lock)) {
+			if (lock_get_wait(lock)
+			    && !lock_rec_has_to_wait_in_queue(lock)) {
 
-			/* Grant the lock */
-			ut_ad(lock->trx != in_lock->trx);
-			lock_grant(lock);
+				/* Grant the lock */
+				ut_ad(lock->trx != in_lock->trx);
+				lock_grant(lock);
+			}
+		}
+	} else {
+		/* Grant locks if there are no conflicting locks ahead.
+		   Move granted locks to the head of the list. */
+		for (lock = lock_rec_get_first_on_page_addr(space, page_no);
+			 lock != NULL;) {
+
+			/* If the lock is a wait lock on this page, and it does not need to wait. */
+			if ((lock->un_member.rec_lock.space == space)
+				&& (lock->un_member.rec_lock.page_no == page_no)
+				&& lock_get_wait(lock)
+				&& !lock_rec_has_to_wait_in_queue(lock)) {
+
+				lock_grant(lock);
+
+				if (previous != NULL) {
+					/* Move the lock to the head of the list. */
+					HASH_GET_NEXT(hash, previous) = HASH_GET_NEXT(hash, lock);
+					lock_rec_move_to_front(lock, rec_fold);
+				} else {
+					/* Already at the head of the list. */
+					previous = lock;
+				}
+				/* Move on to the next lock. */
+				lock = static_cast<lock_t *>(HASH_GET_NEXT(hash, previous));
+			} else {
+				previous = lock;
+				lock = static_cast<lock_t *>(HASH_GET_NEXT(hash, lock));
+			}
 		}
 	}
 }
@@ -4118,7 +4264,8 @@ lock_get_first_lock(
 	}
 
 	ut_a(lock != NULL);
-	ut_a(lock != ctx->wait_lock);
+	ut_a(lock != ctx->wait_lock ||
+            innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS);
 	ut_ad(lock_get_type_low(lock) == lock_get_type_low(ctx->wait_lock));
 
 	return(lock);
@@ -6350,8 +6497,10 @@ lock_rec_queue_validate(
 			        mode, 0, 0, block, heap_no, lock->trx->id));
 #endif /* WITH_WSREP */
 
-		} else if (lock_get_wait(lock) && !lock_rec_get_gap(lock)) {
-
+		} else if (lock_get_wait(lock) && !lock_rec_get_gap(lock)
+				   && innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS) {
+			// If using VATS, it's possible that a wait lock is inserted to a place in the list
+			// such that it does not need to wait.
 			ut_a(lock_rec_has_to_wait_in_queue(lock));
 		}
 	}