linux-kernel - [PATCH 3.14 113/122] mm, compaction: terminate async compaction when rescheduling

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Date:	Wed, 19 Nov 2014 12:52:43 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Rientjes <rientjes@...gle.com>,
	Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH 3.14 113/122] mm, compaction: terminate async compaction when rescheduling

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: David Rientjes <rientjes@...gle.com>

commit aeef4b83806f49a0c454b7d4578671b71045bee2 upstream.

Async compaction terminates prematurely when need_resched(), see
compact_checklock_irqsave().  This can never trigger, however, if the
cond_resched() in isolate_migratepages_range() always takes care of the
scheduling.

If the cond_resched() actually triggers, then terminate this pageblock
scan for async compaction as well.

Signed-off-by: David Rientjes <rientjes@...gle.com>
Acked-by: Mel Gorman <mgorman@...e.de>
Acked-by: Vlastimil Babka <vbabka@...e.cz>
Cc: Mel Gorman <mgorman@...e.de>
Cc: Vlastimil Babka <vbabka@...e.cz>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Mel Gorman <mgorman@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 mm/compaction.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -494,8 +494,13 @@ isolate_migratepages_range(struct zone *
 			return 0;
 	}
 
+	if (cond_resched()) {
+		/* Async terminates prematurely on need_resched() */
+		if (cc->mode == MIGRATE_ASYNC)
+			return 0;
+	}
+
 	/* Time to isolate some pages for migration */
-	cond_resched();
 	for (; low_pfn < end_pfn; low_pfn++) {
 		/* give a chance to irqs before checking need_resched() */
 		if (locked && !(low_pfn % SWAP_CLUSTER_MAX)) {


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