From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757292AbZGPDVg (ORCPT ); Wed, 15 Jul 2009 23:21:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757271AbZGPDVg (ORCPT ); Wed, 15 Jul 2009 23:21:36 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:60271 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757243AbZGPDVf (ORCPT ); Wed, 15 Jul 2009 23:21:35 -0400 Date: Wed, 15 Jul 2009 20:21:14 -0700 From: Andrew Morton To: Rik van Riel Cc: KOSAKI Motohiro , LKML , linux-mm , Wu Fengguang 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> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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