From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762052AbbA3Meh (ORCPT ); Fri, 30 Jan 2015 07:34:37 -0500 Received: from mail-pa0-f43.google.com ([209.85.220.43]:45552 "EHLO mail-pa0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761899AbbA3Mee (ORCPT ); Fri, 30 Jan 2015 07:34:34 -0500 From: Joonsoo Kim X-Google-Original-From: Joonsoo Kim To: Andrew Morton Cc: Vlastimil Babka , Mel Gorman , David Rientjes , Rik van Riel , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Joonsoo Kim , Subject: [PATCH v2 1/4] mm/compaction: fix wrong order check in compact_finished() Date: Fri, 30 Jan 2015 21:34:09 +0900 Message-Id: <1422621252-29859-2-git-send-email-iamjoonsoo.kim@lge.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1422621252-29859-1-git-send-email-iamjoonsoo.kim@lge.com> References: <1422621252-29859-1-git-send-email-iamjoonsoo.kim@lge.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Cc: Acked-by: Vlastimil Babka Signed-off-by: Joonsoo Kim --- mm/compaction.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/compaction.c b/mm/compaction.c index b68736c..4954e19 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -1173,7 +1173,7 @@ static int __compact_finished(struct zone *zone, struct compact_control *cc, 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; } -- 1.9.1