From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933905AbbCFKbS (ORCPT ); Fri, 6 Mar 2015 05:31:18 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44526 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932266AbbCFKAU (ORCPT ); Fri, 6 Mar 2015 05:00:20 -0500 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Joonsoo Kim , Mel Gorman , David Rientjes , Rik van Riel , Andrew Morton , Linus Torvalds , Luis Henriques Subject: [PATCH 3.16.y-ckt 108/183] mm/compaction: fix wrong order check in compact_finished() Date: Fri, 6 Mar 2015 09:56:39 +0000 Message-Id: <1425635874-19087-109-git-send-email-luis.henriques@canonical.com> X-Mailer: git-send-email 2.1.4 In-Reply-To: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> References: <1425635874-19087-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.7-ckt8 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Joonsoo Kim commit 372549c2a3778fd3df445819811c944ad54609ca upstream. What we want to check here is whether there is highorder freepage in buddy list of other migratetype in order to steal it without fragmentation. But, current code just checks cc->order which means allocation request order. So, this is wrong. Without this fix, non-movable synchronous compaction below pageblock order would not stopped until compaction is complete, because migratetype of most pageblocks are movable and high order freepage made by compaction is usually on movable type buddy list. There is some report related to this bug. See below link. http://www.spinics.net/lists/linux-mm/msg81666.html Although the issued system still has load spike comes from compaction, this makes that system completely stable and responsive according to his report. stress-highalloc test in mmtests with non movable order 7 allocation doesn't show any notable difference in allocation success rate, but, it shows more compaction success rate. Compaction success rate (Compaction success * 100 / Compaction stalls, %) 18.47 : 28.94 Fixes: 1fb3f8ca0e92 ("mm: compaction: capture a suitable high-order page immediately when it is made available") Signed-off-by: Joonsoo Kim Acked-by: Vlastimil Babka Reviewed-by: Zhang Yanfei Cc: Mel Gorman Cc: David Rientjes Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Luis Henriques --- mm/compaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index 21bf292b642a..c7c6ae59f787 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -937,7 +937,7 @@ static int compact_finished(struct zone *zone, return COMPACT_PARTIAL; /* Job done if allocation would set block type */ - if (cc->order >= pageblock_order && area->nr_free) + if (order >= pageblock_order && area->nr_free) return COMPACT_PARTIAL; }