From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id C7A3E6B005A for ; Wed, 15 Jul 2009 23:21:13 -0400 (EDT) Date: Wed, 15 Jul 2009 20:21:14 -0700 From: Andrew Morton Subject: Re: [PATCH -mm] throttle direct reclaim when too many pages are isolated already Message-Id: <20090715202114.789d36f7.akpm@linux-foundation.org> In-Reply-To: <4A5E9A33.3030704@redhat.com> References: <20090715223854.7548740a@bree.surriel.com> <20090715194820.237a4d77.akpm@linux-foundation.org> <4A5E9A33.3030704@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Rik van Riel Cc: KOSAKI Motohiro , LKML , linux-mm , Wu Fengguang List-ID: On Wed, 15 Jul 2009 23:10:43 -0400 Rik van Riel wrote: > Andrew Morton wrote: > > On Wed, 15 Jul 2009 22:38:53 -0400 Rik van Riel wrote: > > > >> When way too many processes go into direct reclaim, it is possible > >> for all of the pages to be taken off the LRU. One result of this > >> is that the next process in the page reclaim code thinks there are > >> no reclaimable pages left and triggers an out of memory kill. > >> > >> One solution to this problem is to never let so many processes into > >> the page reclaim path that the entire LRU is emptied. Limiting the > >> system to only having half of each inactive list isolated for > >> reclaim should be safe. > >> > > > > Since when? Linux page reclaim has a bilion machine years testing and > > now stuff like this turns up. Did we break it or is this a > > never-before-discovered workload? > > It's been there for years, in various forms. It hardly ever > shows up, but Kosaki's patch series give us a nice chance to > fix it for good. OK. > >> @@ -1049,6 +1070,10 @@ static unsigned long shrink_inactive_lis > >> struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); > >> int lumpy_reclaim = 0; > >> > >> + while (unlikely(too_many_isolated(zone, file))) { > >> + schedule_timeout_interruptible(HZ/10); > >> + } > > > > This (incorrectly-laid-out) code is a no-op if signal_pending(). > > Good point, I should add some code to break out of page reclaim > if a fatal signal is pending, We can't just return NULL from __alloc_pages(), and if we can't get a page from the freelists then we're just going to have to keep reclaiming. So I'm not sure how we can do this. > and use a normal schedule_timeout > otherwise. congestion_wait() would be typical. > Btw, how is this laid out wrong? How do I do this better? ask checkpatch ;) WARNING: braces {} are not necessary for single statement blocks #99: FILE: mm/vmscan.c:1073: + while (unlikely(too_many_isolated(zone, file))) { + schedule_timeout_interruptible(HZ/10); + } total: 0 errors, 1 warnings, 37 lines checked -- 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/ . Don't email: email@kvack.org