From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx110.postini.com [74.125.245.110]) by kanga.kvack.org (Postfix) with SMTP id D0BA36B004D for ; Thu, 5 Jan 2012 06:20:13 -0500 (EST) Message-ID: <4F0587B0.8000006@freescale.com> Date: Thu, 5 Jan 2012 19:21:20 +0800 From: Huang Shijie MIME-Version: 1.0 Subject: Re: [PATCH] mm/compaction : check the watermark when cc->order is -1 References: <1325312323-13565-1-git-send-email-b32955@freescale.com> <20120105105308.GF28031@suse.de> In-Reply-To: <20120105105308.GF28031@suse.de> Content-Type: text/plain; charset="ISO-8859-15"; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Mel Gorman Cc: akpm@linux-foundation.org, linux-mm@kvack.org > On Sat, Dec 31, 2011 at 02:18:43PM +0800, Huang Shijie wrote: >> We get cc->order is -1 when user echos to /proc/sys/vm/compact_memory. >> In this case, we should check that if we have enough pages for >> the compaction in the zone. >> >> If we do not check this, in our MX6Q board(arm), i ever observed >> COMPACT_CLUSTER_MAX pages were compaction failed in per migrate_pages(). >> That's mean we can not alloc any pages by the free scanner in the zone. >> >> This patch checks the watermark to avoid this problem. >> >> Signed-off-by: Huang Shijie >> --- >> mm/compaction.c | 14 ++++++++++++-- >> 1 files changed, 12 insertions(+), 2 deletions(-) >> >> diff --git a/mm/compaction.c b/mm/compaction.c >> index 899d956..0f12cc9 100644 >> --- a/mm/compaction.c >> +++ b/mm/compaction.c >> @@ -442,8 +442,13 @@ static int compact_finished(struct zone *zone, >> * order == -1 is expected when compacting via >> * /proc/sys/vm/compact_memory >> */ >> - if (cc->order == -1) >> + if (cc->order == -1) { >> + /* Check if we have enough pages now. */ >> + watermark = low_wmark_pages(zone) + COMPACT_CLUSTER_MAX * 2; >> + if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) >> + return COMPACT_SKIPPED; >> return COMPACT_CONTINUE; >> + } >> > We already do the watermark check in compact_finished. Would moving > the cc->order == -1 check below it not be functionally equivalent? This Now, I think these code for compact_finish() is not needed. These lines can be removed. The watermark check in the compaction_suitable() is enough to avoid the problem. Huang Shijie > would be preferable to duplicating the code for the watermark check. > > Same for the second check in your patch. > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org