linux-kernel - [PATCH] mm: compaction: Do not compact pgdat for order-0

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Message-ID: <20130815153927.GZ2296@suse.de>
Date:	Thu, 15 Aug 2013 16:39:27 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Hillf Danton <dhillf@...il.com>, Minchan Kim <minchan@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: [PATCH] mm: compaction: Do not compact pgdat for order-0

If kswapd was reclaiming for a high order and resets it to 0 due to
fragmentation it will still call compact_pgdat. For the most part, this will
fail a compaction_suitable() test and not compact but it is unnecessarily
sloppy. It could be fixed in the caller but fix it in the API instead.

[dhillf@...il.com: Pointed out that it was a potential problem]
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 mm/compaction.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index 05ccb4c..c437893 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1131,6 +1131,9 @@ void compact_pgdat(pg_data_t *pgdat, int order)
 		.sync = false,
 	};
 
+	if (!order)
+		return;
+
 	__compact_pgdat(pgdat, &cc);
 }
 
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