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Message-ID: <alpine.DEB.2.02.1309041625060.29607@chino.kir.corp.google.com>
Date: Wed, 4 Sep 2013 16:25:59 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org
Subject: [patch] mm, compaction: periodically schedule when freeing pages
We've been getting warnings about an excessive amount of time spent
allocating pages for migration during memory compaction without
scheduling. isolate_freepages_block() already periodically checks for
contended locks or the need to schedule, but isolate_freepages() never
does.
When a zone is massively long and no suitable targets can be found, this
iteration can be quite expensive without ever doing cond_resched().
Check periodically for the need to reschedule while the compaction free
scanner iterates.
Signed-off-by: David Rientjes <rientjes@...gle.com>
---
mm/compaction.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -677,6 +677,13 @@ static void isolate_freepages(struct zone *zone,
pfn -= pageblock_nr_pages) {
unsigned long isolated;
+ /*
+ * This can iterate a massively long zone without finding any
+ * suitable migration targets, so periodically check if we need
+ * to schedule.
+ */
+ cond_resched();
+
if (!pfn_valid(pfn))
continue;
--
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