path: root/mm/vmscan.c
diff options
authorShaohua Li <shaohua.li@intel.com>2011-10-31 17:07:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-10-31 17:30:45 -0700
commit3da367c3e5fca71d4e778fa565d9b098d5518f4a (patch)
tree915dff1989bdffaed157b56f724631b5d8f2d328 /mm/vmscan.c
parent3fa36acbced23c563345de3179dfe1775f15be5e (diff)
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 <shaohua.li@intel.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Minchan Kim <minchan.kim@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/vmscan.c')
1 files changed, 3 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c
index b68a9342d5a..b1520b07785 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;
nr_reclaimed = 0;
nr_scanned = sc->nr_scanned;
get_scan_count(zone, sc, nr, priority);
+ blk_start_plug(&plug);
for_each_evictable_lru(l) {
@@ -2034,6 +2036,7 @@ restart:
if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY)
+ blk_finish_plug(&plug);
sc->nr_reclaimed += nr_reclaimed;