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authorMel Gorman <mgorman@suse.de>2013-01-11 09:27:01 +0000
committerLinus Torvalds <torvalds@linux-foundation.org>2013-01-11 09:02:00 -0800
commit47ecfcb7d01418fcbfbc75183ba5e28e98b667b2 (patch)
treec3ca70fb0d9a09248d4cdcdf6a006c36359e8665 /mm/internal.h
parent254adaa465c40151df11fc1f88f93e6e86eb61d4 (diff)
downloadlinux-47ecfcb7d01418fcbfbc75183ba5e28e98b667b2.tar.bz2
mm: compaction: Partially revert capture of suitable high-order page
Eric Wong reported on 3.7 and 3.8-rc2 that ppoll() got stuck when waiting for POLLIN on a local TCP socket. It was easier to trigger if there was disk IO and dirty pages at the same time and he bisected it to commit 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available"). The intention of that patch was to improve high-order allocations under memory pressure after changes made to reclaim in 3.6 drastically hurt THP allocations but the approach was flawed. For Eric, the problem was that page->pfmemalloc was not being cleared for captured pages leading to a poor interaction with swap-over-NFS support causing the packets to be dropped. However, I identified a few more problems with the patch including the fact that it can increase contention on zone->lock in some cases which could result in async direct compaction being aborted early. In retrospect the capture patch took the wrong approach. What it should have done is mark the pageblock being migrated as MIGRATE_ISOLATE if it was allocating for THP and avoided races that way. While the patch was showing to improve allocation success rates at the time, the benefit is marginal given the relative complexity and it should be revisited from scratch in the context of the other reclaim-related changes that have taken place since the patch was first written and tested. This patch partially reverts commit 1fb3f8ca "mm: compaction: capture a suitable high-order page immediately when it is made available". Reported-and-tested-by: Eric Wong <normalperson@yhbt.net> Tested-by: Eric Dumazet <eric.dumazet@gmail.com> Cc: stable@vger.kernel.org Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/internal.h')
-rw-r--r--mm/internal.h1
1 files changed, 0 insertions, 1 deletions
diff --git a/mm/internal.h b/mm/internal.h
index d597f94cc205..9ba21100ebf3 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -135,7 +135,6 @@ struct compact_control {
int migratetype; /* MOVABLE, RECLAIMABLE etc */
struct zone *zone;
bool contended; /* True if a lock was contended */
- struct page **page; /* Page captured of requested size */
};
unsigned long