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Commit e0c23279 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds
Browse files

vmscan: abort reclaim/compaction if compaction can proceed 



If compaction can proceed, shrink_zones() stops doing any work but its
callers still call shrink_slab() which raises the priority and potentially
sleeps.  This is unnecessary and wasteful so this patch aborts direct
reclaim/compaction entirely if compaction can proceed.

Signed-off-by: default avatarMel Gorman <mgorman@suse.de>
Acked-by: default avatarRik van Riel <riel@redhat.com>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Acked-by: default avatarJohannes Weiner <jweiner@redhat.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e0887c19

mm/vmscan.c

+21 −11
Original line number Diff line number Diff line
@@ -2103,14 +2103,19 @@ static void shrink_zone(int priority, struct zone *zone, 
 *

 * If a zone is deemed to be full of pinned pages then just give it a light

 * scan then give up on it.

 *

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

 * high-order allocation and compaction is either ready to begin or deferred.

 * This indicates to the caller that it should retry the allocation or fail.

 */

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

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

					struct scan_control *sc)

{

	struct zoneref *z;

	struct zone *zone;

	unsigned long nr_soft_reclaimed;

	unsigned long nr_soft_scanned;

	bool should_abort_reclaim = false;



	for_each_zone_zonelist_nodemask(zone, z, zonelist,

					gfp_zone(sc->gfp_mask), sc->nodemask) {
@@ -2127,20 +2132,21 @@ static void shrink_zones(int priority, struct zonelist *zonelist, 
				continue;	/* Let kswapd poll it */

			if (COMPACTION_BUILD) {

				/*

				 * If we already have plenty of memory

				 * free for compaction, don't free any

				 * more.  Even though compaction is

				 * invoked for any non-zero order,

				 * only frequent costly order

				 * reclamation is disruptive enough to

				 * become a noticable problem, like

				 * transparent huge page allocations.

				 * If we already have plenty of memory free for

				 * compaction in this zone, don't free any more.

				 * Even though compaction is invoked for any

				 * non-zero order, only frequent costly order

				 * reclamation is disruptive enough to become a

				 * noticable problem, like transparent huge page

				 * allocations.

				 */

				if (sc->order > PAGE_ALLOC_COSTLY_ORDER &&

					(compaction_suitable(zone, sc->order) ||

					 compaction_deferred(zone)))

					 compaction_deferred(zone))) {

					should_abort_reclaim = true;

					continue;

				}

			}

			/*

			 * This steals pages from memory cgroups over softlimit

			 * and returns the number of reclaimed pages and
@@ -2158,6 +2164,8 @@ static void shrink_zones(int priority, struct zonelist *zonelist, 


		shrink_zone(priority, zone, sc);

	}



	return should_abort_reclaim;

}



static bool zone_reclaimable(struct zone *zone)
@@ -2222,7 +2230,9 @@ static unsigned long do_try_to_free_pages(struct zonelist *zonelist, 
		sc->nr_scanned = 0;

		if (!priority)

			disable_swap_token(sc->mem_cgroup);

		shrink_zones(priority, zonelist, sc);

		if (shrink_zones(priority, zonelist, sc))

			break;



		/*

		 * Don't shrink slabs when reclaiming memory from

		 * over limit cgroups