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 D97A76B016A for ; Fri, 26 Aug 2011 03:35:19 -0400 (EDT) Message-ID: <4E574CA5.4010701@openvz.org> Date: Fri, 26 Aug 2011 11:35:01 +0400 From: Konstantin Khlebnikov MIME-Version: 1.0 Subject: Re: [PATCH] oom: skip frozen tasks References: <20110823073101.6426.77745.stgit@zurg> <20110824101927.GB3505@tiehlicka.suse.cz> <20110825091920.GA22564@tiehlicka.suse.cz> <20110825151818.GA4003@redhat.com> <20110825164758.GB22564@tiehlicka.suse.cz> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: David Rientjes Cc: Michal Hocko , Oleg Nesterov , "linux-mm@kvack.org" , Andrew Morton , "linux-kernel@vger.kernel.org" , KOSAKI Motohiro , KAMEZAWA Hiroyuki , "Rafael J. Wysocki" David Rientjes wrote: > On Thu, 25 Aug 2011, Michal Hocko wrote: > >>>>> That's obviously false since we call oom_killer_disable() in >>>>> freeze_processes() to disable the oom killer from ever being called in the >>>>> first place, so this is something you need to resolve with Rafael before >>>>> you cause more machines to panic. >>>> >>>> I didn't mean suspend/resume path (that is protected by oom_killer_disabled) >>>> so the patch doesn't make any change. >>> >>> Confused... freeze_processes() does try_to_freeze_tasks() before >>> oom_killer_disable() ? >> >> Yes you are right, I must have been blind. >> >> Now I see the point. We do not want to panic while we are suspending and >> the memory is really low just because all the userspace is already in >> the the fridge. >> Sorry for confusion. >> >> I still do not follow the oom_killer_disable note from David, though. >> > > oom_killer_disable() was added to that path for a reason when all threads > are frozen: memory allocations still occur in the suspend path in an oom > condition and adding the oom_killer_disable() will cause those > allocations to fail rather than sending pointless SIGKILLs to frozen > threads. > > Now consider if the only _eligible_ threads for oom kill (because of > cpusets or mempolicies) are those that are frozen. We certainly do not > want to panic because other cpusets are still getting work done. We'd > either want to add a mem to the cpuset or thaw the processes because the > cpuset is oom. > > You can't just selectively skip certain threads when their state can be > temporary without risking a panic. That's why this patch is a > non-starter. > > A much better solution would be to lower the badness score that the oom > killer uses for PF_FROZEN threads so that they aren't considered a > priority for kill unless there's nothing else left to kill. Anyway, oom killer shouldn't loop endlessly if it see TIF_MEMDIE on frozen task, it must go on and try to kill somebody else. We cannot wait for thawing this task. -- 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