[PATCH 2/2] mm: Abort reclaim/compaction if compaction can proceed

Mel Gorman
2011-10-07T15:17:47Z

If compaction can proceed, shrink_zones() stops doing any work but
the callers still shrink_slab(), raises the priority and potentially
sleeps. This patch aborts direct reclaim/compaction entirely if
compaction can proceed.

Signed-off-by: Mel Gorman <mgorman@suse.de>
---
mm/vmscan.c | 20 ++++++++++++++++----
1 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 3817fa9..522f205 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2044,14 +2044,19 @@ 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) {
@@ -2069,12 +2074,15 @@ static void shrink_zones(int priority, struct zonelist *zonelist,
if (COMPACTION_BUILD) {
/*
* If we already have plenty of memory free
- * for compaction, don't free any more.
+ * for compaction in this zone , don't free any
+ * more.
*/
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
@@ -2093,6 +2101,8 @@ 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)
@@ -2157,7 +2167,9 @@ 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
--
1.7.3.4