commit 6532572a783ea5a025561eda9b1a9350c73405a6
Author: Nickolay Ihalainen <ihanick@gmail.com>
Date:   Wed Nov 25 10:17:30 2015 +0300

    Partial fix for lp:1433432, avoid redundant CPU spinning in the LRU manager thread when previous iteration isn't able to flush.
    Deadlock with innodb_empty_free_list_algorithm=backoff is not resolved.

diff --git a/storage/innobase/buf/buf0flu.cc b/storage/innobase/buf/buf0flu.cc
index d9893fc..97c86ee 100644
--- a/storage/innobase/buf/buf0flu.cc
+++ b/storage/innobase/buf/buf0flu.cc
@@ -2209,9 +2209,10 @@ Clears up tail of the LRU lists:
 * Put replaceable pages at the tail of LRU to the free list
 * Flush dirty pages at the tail of LRU to the disk
 The depth to which we scan each buffer pool is controlled by dynamic
-config parameter innodb_LRU_scan_depth. */
+config parameter innodb_LRU_scan_depth.
+@return number of pages flushed */
 UNIV_INTERN
-void
+ulint
 buf_flush_LRU_tail(void)
 /*====================*/
 {
@@ -2313,6 +2314,7 @@ buf_flush_LRU_tail(void)
 			MONITOR_LRU_BATCH_PAGES,
 			total_flushed);
 	}
+	return(total_flushed);
 }
 
 /*********************************************************************//**
@@ -2608,19 +2610,24 @@ static
 void
 page_cleaner_adapt_lru_sleep_time(
 /*==============================*/
-	ulint*	lru_sleep_time)	/*!< in/out: desired page cleaner thread sleep
+	ulint*	lru_sleep_time,	/*!< in/out: desired page cleaner thread sleep
 				time for LRU flushes  */
+	ulint	lru_n_flushed) /*!< in: number of flushed in previous batch */
+
 {
 	ulint free_len = buf_get_total_free_list_length();
 	ulint max_free_len = srv_LRU_scan_depth * srv_buf_pool_instances;
 
-	if (free_len < max_free_len / 100) {
+	if (free_len < max_free_len / 100 && lru_n_flushed) {
 
-		/* Free lists filled less than 1%, no sleep */
+		/* Free lists filled less than 1%
+		and iteration was able to flush, no sleep */
 		*lru_sleep_time = 0;
-	} else if (free_len > max_free_len / 5) {
+	} else if (free_len > max_free_len / 5
+		   || (free_len < max_free_len / 100 && lru_n_flushed == 0)) {
 
-		/* Free lists filled more than 20%, sleep a bit more */
+		/* Free lists filled more than 20%
+		or no pages flushed in previous batch, sleep a bit more */
 		*lru_sleep_time += 50;
 		if (*lru_sleep_time > srv_cleaner_max_lru_time)
 			*lru_sleep_time = srv_cleaner_max_lru_time;
@@ -2826,6 +2833,7 @@ DECLARE_THREAD(buf_flush_lru_manager_thread)(
 {
 	ulint	next_loop_time = ut_time_ms() + 1000;
 	ulint	lru_sleep_time = srv_cleaner_max_lru_time;
+	ulint	lru_n_flushed = 1;
 
 #ifdef UNIV_PFS_THREAD
 	pfs_register_thread(buf_lru_manager_thread_key);
@@ -2852,11 +2860,11 @@ DECLARE_THREAD(buf_flush_lru_manager_thread)(
 
 		page_cleaner_sleep_if_needed(next_loop_time);
 
-		page_cleaner_adapt_lru_sleep_time(&lru_sleep_time);
+		page_cleaner_adapt_lru_sleep_time(&lru_sleep_time, lru_n_flushed);
 
 		next_loop_time = ut_time_ms() + lru_sleep_time;
 
-		buf_flush_LRU_tail();
+		lru_n_flushed = buf_flush_LRU_tail();
 	}
 
 	buf_lru_manager_is_active = false;
diff --git a/storage/innobase/include/buf0flu.h b/storage/innobase/include/buf0flu.h
index b73037d..2cd8eef 100644
--- a/storage/innobase/include/buf0flu.h
+++ b/storage/innobase/include/buf0flu.h
@@ -202,9 +202,10 @@ Clears up tail of the LRU lists:
 * Put replaceable pages at the tail of LRU to the free list
 * Flush dirty pages at the tail of LRU to the disk
 The depth to which we scan each buffer pool is controlled by dynamic
-config parameter innodb_LRU_scan_depth. */
+config parameter innodb_LRU_scan_depth.
+@return number of pages flushed */
 UNIV_INTERN
-void
+ulint
 buf_flush_LRU_tail(void);
 /*====================*/
 /*********************************************************************//**