mm: vmscan: do not allow kswapd to scan at maximum priority
authorMel Gorman <mgorman@suse.de>
Wed, 3 Jul 2013 22:01:48 +0000 (15:01 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Wed, 3 Jul 2013 23:07:28 +0000 (16:07 -0700)
commit9aa41348a8d11427feec350b21dcdd4330fd20c4
tree139e778569caa811bcfe904c03bb5fcf784dd258
parent2ab44f434586b8ccb11f781b4c2730492e6628f5
mm: vmscan: do not allow kswapd to scan at maximum priority

Page reclaim at priority 0 will scan the entire LRU as priority 0 is
considered to be a near OOM condition.  Kswapd can reach priority 0
quite easily if it is encountering a large number of pages it cannot
reclaim such as pages under writeback.  When this happens, kswapd
reclaims very aggressively even though there may be no real risk of
allocation failure or OOM.

This patch prevents kswapd reaching priority 0 and trying to reclaim the
world.  Direct reclaimers will still reach priority 0 in the event of an
OOM situation.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Valdis Kletnieks <Valdis.Kletnieks@vt.edu>
Tested-by: Zlatko Calusic <zcalusic@bitsync.net>
Cc: dormando <dormando@rydia.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/vmscan.c