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Commit 0cee34fd authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

mm: vmscan: check if reclaim should really abort even if compaction_ready() is true for one zone 



If compaction can proceed for a given zone, shrink_zones() does not
reclaim any more pages from it.  After commit [e0c23279: vmscan: abort
reclaim/compaction if compaction can proceed], do_try_to_free_pages()
tries to finish as soon as possible once one zone can compact.

This was intended to prevent slabs being shrunk unnecessarily but there
are side-effects.  One is that a small zone that is ready for compaction
will abort reclaim even if the chances of successfully allocating a THP
from that zone is small.  It also means that reclaim can return too early
even though sc->nr_to_reclaim pages were not reclaimed.

This partially reverts the commit until it is proven that slabs are really
being shrunk unnecessarily but preserves the check to return 1 to avoid
OOM if reclaim was aborted prematurely.

[aarcange@redhat.com: This patch replaces a revert from Andrea]
Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Reviewed-by: default avatarRik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Dave Jones <davej@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Andy Isaacson <adi@hexapodia.org>
Cc: Nai Xia <nai.xia@gmail.com>
Cc: Johannes Weiner <jweiner@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent fe4b1b24

mm/vmscan.c

+9 −10
Original line number Diff line number Diff line
@@ -2217,7 +2217,8 @@ static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) 
 *

 * This function returns true if a zone is being reclaimed for a costly

 * high-order allocation and compaction is ready to begin. This indicates to

 * the caller that it should retry the allocation or fail.

 * the caller that it should consider retrying the allocation instead of

 * further reclaim.

 */

static bool shrink_zones(int priority, struct zonelist *zonelist,

					struct scan_control *sc)
@@ -2226,7 +2227,7 @@ static bool shrink_zones(int priority, struct zonelist *zonelist, 
	struct zone *zone;

	unsigned long nr_soft_reclaimed;

	unsigned long nr_soft_scanned;

	bool should_abort_reclaim = false;

	bool aborted_reclaim = false;



	for_each_zone_zonelist_nodemask(zone, z, zonelist,

					gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -2252,7 +2253,7 @@ static bool shrink_zones(int priority, struct zonelist *zonelist, 
				 * allocations.

				 */

				if (compaction_ready(zone, sc)) {

					should_abort_reclaim = true;

					aborted_reclaim = true;

					continue;

				}

			}
@@ -2274,7 +2275,7 @@ static bool shrink_zones(int priority, struct zonelist *zonelist, 
		shrink_zone(priority, zone, sc);

	}



	return should_abort_reclaim;

	return aborted_reclaim;

}



static bool zone_reclaimable(struct zone *zone)
@@ -2328,7 +2329,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 
	struct zoneref *z;

	struct zone *zone;

	unsigned long writeback_threshold;

	bool should_abort_reclaim;

	bool aborted_reclaim;



	get_mems_allowed();

	delayacct_freepages_start();
@@ -2340,9 +2341,7 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 
		sc->nr_scanned = 0;

		if (!priority)

			disable_swap_token(sc->target_mem_cgroup);

		should_abort_reclaim = shrink_zones(priority, zonelist, sc);

		if (should_abort_reclaim)

			break;

		aborted_reclaim = shrink_zones(priority, zonelist, sc);



		/*

		 * Don't shrink slabs when reclaiming memory from
@@ -2409,8 +2408,8 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 
	if (oom_killer_disabled)

		return 0;



	/* Aborting reclaim to try compaction? don't OOM, then */

	if (should_abort_reclaim)

	/* Aborted reclaim to try compaction? don't OOM, then */

	if (aborted_reclaim)

		return 1;



	/* top priority shrink_zones still had more to do? don't OOM, then */