From: Shaohua Li Date: Tue, 1 Nov 2011 00:07:03 +0000 (-0700) Subject: vmscan: add block plug for page reclaim X-Git-Tag: upstream/snapshot3+hdmi~8868^2~115 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=3da367c3e5fca71d4e778fa565d9b098d5518f4a;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git vmscan: add block plug for page reclaim per-task block plug can reduce block queue lock contention and increase request merge. Currently page reclaim doesn't support it. I originally thought page reclaim doesn't need it, because kswapd thread count is limited and file cache write is done at flusher mostly. When I test a workload with heavy swap in a 4-node machine, each CPU is doing direct page reclaim and swap. This causes block queue lock contention. In my test, without below patch, the CPU utilization is about 2% ~ 7%. With the patch, the CPU utilization is about 1% ~ 3%. Disk throughput isn't changed. This should improve normal kswapd write and file cache write too (increase request merge for example), but might not be so obvious as I explain above. Signed-off-by: Shaohua Li Cc: Jens Axboe Cc: Minchan Kim Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/vmscan.c b/mm/vmscan.c index b68a934..b1520b0 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -2005,12 +2005,14 @@ static void shrink_zone(int priority, struct zone *zone, enum lru_list l; unsigned long nr_reclaimed, nr_scanned; unsigned long nr_to_reclaim = sc->nr_to_reclaim; + struct blk_plug plug; restart: nr_reclaimed = 0; nr_scanned = sc->nr_scanned; get_scan_count(zone, sc, nr, priority); + blk_start_plug(&plug); while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || nr[LRU_INACTIVE_FILE]) { for_each_evictable_lru(l) { @@ -2034,6 +2036,7 @@ restart: if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) break; } + blk_finish_plug(&plug); sc->nr_reclaimed += nr_reclaimed; /*