Fix bug https://code.launchpad.net/~laurynas-biveinis/percona-server/bug1295268

(Inadequate background LRU flushing for write workloads with InnoDB compression).
  
  If InnoDB compression is used and the workload has writes, the
  following situation is possible. The LRU flusher issues an LRU flush
  request for an instance.  buf_do_LRU_batch decides to perform
  unzip_LRU eviction and this eviction might fully satisfy the
  request. Then buf_flush_LRU_tail checks the number of flushed pages in
  the last iteration, finds it to be zero, and wrongly decides not to
  flush that instance anymore.
  
  Fixed by maintaining unzip_LRU eviction counter in struct
  flush_counter_t variables, and checking it in buf_flush_LRU_tail when
  deciding whether to stop flushing the current instance.

Added test cases for new configuration files to get mysql-test-run suite sys_vars
to pass. Fix some small errors.

1 files changed, 16 insertions, 8 deletions

diff --git a/storage/xtradb/buf/buf0flu.cc b/storage/xtradb/buf/buf0flu.cc
index 53ac9bb9cc7..f4ba0f10761 100644
--- a/storage/xtradb/buf/buf0flu.cc
+++ b/storage/xtradb/buf/buf0flu.cc
@@ -1549,6 +1549,7 @@ buf_flush_LRU_list_batch(
 
 	n->flushed = 0;
 	n->evicted = 0;
+	n->unzip_LRU_evicted = 0;
 
 	ut_ad(mutex_own(&buf_pool->LRU_list_mutex));
 
@@ -1660,21 +1661,22 @@ buf_do_LRU_batch(
 	flush_counters_t*	n)	/*!< out: flushed/evicted page
 					counts */
 {
-	ulint	count = 0;
-
 	if (buf_LRU_evict_from_unzip_LRU(buf_pool)) {
-		count += buf_free_from_unzip_LRU_list_batch(buf_pool, max);
+		n->unzip_LRU_evicted
+			+= buf_free_from_unzip_LRU_list_batch(buf_pool, max);
+	} else {
+		n->unzip_LRU_evicted = 0;
 	}
 
-	if (max > count) {
-		buf_flush_LRU_list_batch(buf_pool, max - count, limited_scan,
-					 n);
+	if (max > n->unzip_LRU_evicted) {
+		buf_flush_LRU_list_batch(buf_pool, max - n->unzip_LRU_evicted,
+					 limited_scan, n);
 	} else {
 		n->evicted = 0;
 		n->flushed = 0;
 	}
 
-	n->flushed += count;
+	n->evicted += n->unzip_LRU_evicted;
 }
 
 /*******************************************************************//**
@@ -2306,9 +2308,15 @@ buf_flush_LRU_tail(void)
 
 				requested_pages[i] += lru_chunk_size;
 
+				/* If we failed to flush or evict this
+				instance, do not bother anymore. But take into
+			        account that we might have zero flushed pages
+				because the flushing request was fully
+				satisfied by unzip_LRU evictions. */
 				if (requested_pages[i] >= scan_depth[i]
 				    || !(srv_cleaner_eviction_factor
-					 ? n.evicted : n.flushed)) {
+					? n.evicted
+					: (n.flushed + n.unzip_LRU_evicted))) {
 
 					active_instance[i] = false;
 					remaining_instances--;