From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with SMTP id 8ED1A6B00D4 for ; Tue, 19 Oct 2010 03:15:47 -0400 (EDT) Date: Tue, 19 Oct 2010 15:15:34 +0800 From: Shaohua Li Subject: Re: Deadlock possibly caused by too_many_isolated. Message-ID: <20101019071534.GA15105@sli10-conroe.sh.intel.com> References: <20101019093142.509d6947@notabene> <20101018154137.90f5325f.akpm@linux-foundation.org> <20101019095144.A1B0.A69D9226@jp.fujitsu.com> <20101019023537.GB8310@localhost> <20101019030515.GB11924@localhost> <20101019032145.GA3108@sli10-conroe.sh.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20101019032145.GA3108@sli10-conroe.sh.intel.com> Sender: owner-linux-mm@kvack.org To: Minchan Kim Cc: "Wu, Fengguang" , KOSAKI Motohiro , Andrew Morton , Neil Brown , Rik van Riel , KAMEZAWA Hiroyuki , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" List-ID: On Tue, Oct 19, 2010 at 11:21:45AM +0800, Shaohua Li wrote: > On Tue, Oct 19, 2010 at 11:09:29AM +0800, Minchan Kim wrote: > > On Tue, Oct 19, 2010 at 12:05 PM, Wu Fengguang wrote: > > > On Tue, Oct 19, 2010 at 10:52:47AM +0800, Minchan Kim wrote: > > >> Hi Wu, > > >> > > >> On Tue, Oct 19, 2010 at 11:35 AM, Wu Fengguang wrote: > > >> >> @@ -2054,10 +2069,11 @@ rebalance: > > >> >> goto got_pg; > > >> >> > > >> >> /* > > >> >> - * If we failed to make any progress reclaiming, then we are > > >> >> - * running out of options and have to consider going OOM > > >> >> + * If we failed to make any progress reclaiming and there aren't > > >> >> + * many parallel reclaiming, then we are unning out of options and > > >> >> + * have to consider going OOM > > >> >> */ > > >> >> - if (!did_some_progress) { > > >> >> + if (!did_some_progress && !too_many_isolated_zone(preferred_zone)) { > > >> >> if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) { > > >> >> if (oom_killer_disabled) > > >> >> goto nopage; > > >> > > > >> > This is simply wrong. > > >> > > > >> > It disabled this block for 99% system because there won't be enough > > >> > tasks to make (!too_many_isolated_zone == true). As a result the LRU > > >> > will be scanned like mad and no task get OOMed when it should be. > > >> > > >> If !too_many_isolated_zone is false, it means there are already many > > >> direct reclaiming tasks. > > >> So they could exit reclaim path and !too_many_isolated_zone will be true. > > >> What am I missing now? > > > > > > Ah sorry, my brain get short circuited.. but I still feel uneasy with > > > this change. It's not fixing the root cause and won't prevent too many > > > LRU pages be isolated. It's too late to test too_many_isolated_zone() > > > after direct reclaim returns (after sleeping for a long time). > > > > > > > Intend to agree. > > I think root cause is a infinite looping in too_many_isolated holding FS lock. > > Would it be simple that too_many_isolated would be bail out after some try? > I'm wondering if we need too_many_isolated_zone logic. The do_try_to_free_pages > will return progress till all zones are unreclaimable. Assume before this we > don't oomkiller. If the direct reclaim fails but has progress, it will sleep. Not sure if this is clear. What I mean is we can delete too_many_isolated_zone, do_try_to_free_pages can still return 1 till all zones are unreclaimable. Before this direct reclaim will not oom, because it sees progress and will call congestion_wait to sleep. Am I missing anything? -- 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