[PATCH 10/34] mm: Abort reclaim/compaction if compaction can proceed

Mel Gorman
2012-07-23T13:39:04Z

commit e0c23279c9f800c403f37511484d9014ac83adec upstream.

Stable note: Not tracked on Bugzilla. THP and compaction was found to
aggressively reclaim pages and stall systems under different
situations that was addressed piecemeal over time.

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: Mel Gorman <mgorman@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Johannes Weiner <jweiner@redhat.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
mm/vmscan.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index d11b6c4..65388ac 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2037,14 +2037,19 @@ restart:
*
* 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) {
@@ -2061,19 +2066,20 @@ 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
@@ -2092,6 +2098,8 @@ 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)
@@ -2156,7 +2164,9 @@ 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
--
1.7.9.2