revert "mm: vmscan: do not swap anon pages just because free+file is low"
authorJohannes Weiner <hannes@cmpxchg.org>
Tue, 6 May 2014 19:50:07 +0000 (12:50 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 6 May 2014 20:04:59 +0000 (13:04 -0700)
commit623762517e2370be3b3f95f4fe08d6c063a49b06
tree94d42e42a3b1eb693ba387b6b297351ef6b03ed2
parent6b6751f7feba68d8f5c72b72cc69a1c5a625529c
revert "mm: vmscan: do not swap anon pages just because free+file is low"

This reverts commit 0bf1457f0cfc ("mm: vmscan: do not swap anon pages
just because free+file is low") because it introduced a regression in
mostly-anonymous workloads, where reclaim would become ineffective and
trap every allocating task in direct reclaim.

The problem is that there is a runaway feedback loop in the scan balance
between file and anon, where the balance tips heavily towards a tiny
thrashing file LRU and anonymous pages are no longer being looked at.
The commit in question removed the safe guard that would detect such
situations and respond with forced anonymous reclaim.

This commit was part of a series to fix premature swapping in loads with
relatively little cache, and while it made a small difference, the cure
is obviously worse than the disease.  Revert it.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Rafael Aquini <aquini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: <stable@kernel.org> [3.12+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/vmscan.c