From: Shaohua Li <shli@kernel.org>
Date: Thu, 13 Sep 2012 01:00:59 +0000 (+1000)
Subject: mm: compaction: abort compaction loop if lock is contended or run too long
X-Git-Tag: next-20120918~1^2~125
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f587083c389efd6ebe4a167053956b39f376782f;p=karo-tx-linux.git

mm: compaction: abort compaction loop if lock is contended or run too long

isolate_migratepages_range() might isolate no pages, for example, when
zone->lru_lock is contended and compaction is async.  In this case, we
should abort compaction, otherwise, compact_zone will run a useless loop
and make zone->lru_lock is even contended.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Shaohua Li <shli@fusionio.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/compaction.c b/mm/compaction.c
index 0fbc6b73a522..6a6bb4b3b18d 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -70,8 +70,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags,
 
 		/* async aborts if taking too long or contended */
 		if (!cc->sync) {
-			if (cc->contended)
-				*cc->contended = true;
+			cc->contended = true;
 			return false;
 		}
 
@@ -688,7 +687,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
 
 	/* Perform the isolation */
 	low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn);
-	if (!low_pfn)
+	if (!low_pfn || cc->contended)
 		return ISOLATE_ABORT;
 
 	cc->migrate_pfn = low_pfn;
@@ -896,6 +895,7 @@ static unsigned long compact_zone_order(struct zone *zone,
 				 bool sync, bool *contended,
 				 struct page **page)
 {
+	unsigned long ret;
 	struct compact_control cc = {
 		.nr_freepages = 0,
 		.nr_migratepages = 0,
@@ -903,13 +903,15 @@ static unsigned long compact_zone_order(struct zone *zone,
 		.migratetype = allocflags_to_migratetype(gfp_mask),
 		.zone = zone,
 		.sync = sync,
-		.contended = contended,
 		.page = page,
 	};
 	INIT_LIST_HEAD(&cc.freepages);
 	INIT_LIST_HEAD(&cc.migratepages);
 
-	return compact_zone(zone, &cc);
+	ret = compact_zone(zone, &cc);
+	if (contended)
+		*contended = cc.contended;
+	return ret;
 }
 
 int sysctl_extfrag_threshold = 500;
diff --git a/mm/internal.h b/mm/internal.h
index 386772f89cfe..eebbed59b85b 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -131,7 +131,7 @@ struct compact_control {
 	int order;			/* order a direct compactor needs */
 	int migratetype;		/* MOVABLE, RECLAIMABLE etc */
 	struct zone *zone;
-	bool *contended;		/* True if a lock was contended */
+	bool contended;			/* True if a lock was contended */
 	struct page **page;		/* Page captured of requested size */
 };