page allocator: always wake kswapd when restarting an allocation attempt after direct...
authorMel Gorman <mel@csn.ul.ie>
Wed, 11 Nov 2009 22:26:14 +0000 (14:26 -0800)
committerGreg Kroah-Hartman <gregkh@suse.de>
Tue, 8 Dec 2009 18:21:23 +0000 (10:21 -0800)
commitffb83b9e7d0e935ccc665ed09f2f7273828c9cfb
treed7b663d6c4e2d1bb848340be49992449a0019ca5
parent88b117ce4ae1a68c5be558c182b1bea1967cac73
page allocator: always wake kswapd when restarting an allocation attempt after direct reclaim failed

commit cc4a6851466039a8a688c843962a05689059ff3b upstream.

If a direct reclaim makes no forward progress, it considers whether it
should go OOM or not.  Whether OOM is triggered or not, it may retry the
allocation afterwards.  In times past, this would always wake kswapd as
well but currently, kswapd is not woken up after direct reclaim fails.
For order-0 allocations, this makes little difference but if there is a
heavy mix of higher-order allocations that direct reclaim is failing for,
it might mean that kswapd is not rewoken for higher orders as much as it
did previously.

This patch wakes up kswapd when an allocation is being retried after a
direct reclaim failure.  It would be expected that kswapd is already
awake, but this has the effect of telling kswapd to reclaim at the higher
order as well.

Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: Christoph Lameter <cl@linux-foundation.org>
Reviewed-by: Pekka Enberg <penberg@cs.helsinki.fi>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
mm/page_alloc.c