From: Michal Hocko <mhocko@suse.cz> To: David Rientjes <rientjes@google.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Oleg Nesterov <oleg@redhat.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Subject: Re: [PATCH] oom: skip frozen tasks Date: Wed, 24 Aug 2011 12:19:27 +0200 [thread overview] Message-ID: <20110824101927.GB3505@tiehlicka.suse.cz> (raw) In-Reply-To: <alpine.DEB.2.00.1108231313520.21637@chino.kir.corp.google.com> On Tue 23-08-11 13:18:14, David Rientjes wrote: > On Tue, 23 Aug 2011, Konstantin Khlebnikov wrote: > > > All frozen tasks are unkillable, and if one of them has TIF_MEMDIE > > we must kill something else to avoid deadlock. After this patch > > select_bad_process() will skip frozen task before checking TIF_MEMDIE. > > > > The caveat is that if the task in the refrigerator is not OOM_DISABLE and > there are no other eligible tasks (system wide, in the cpuset, or in the > memcg) to kill, then the machine will panic as a result of this when, in > the past, we would simply issue the SIGKILL and keep looping in the page > allocator until it is thawed. mem_cgroup_out_of_memory doesn't panic if nothing has been selected. We will loop in the charge&reclaim path until somebody frees some memory. > So you may actually be trading a stall waiting for this thread to thaw for > what would now be a panic, and that's not clearly better to me. When we are in the global OOM condition then you are right, we have a higher chance to panic. I still find the patch an improvement because encountering a frozen task and looping over it without any progress (even though there are other tasks that could be killed) is more probable than having no killable task at all. On non-NUMA machines there is even not a big chance that somebody would be able to thaw a task as the system is already on knees. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@suse.cz> To: David Rientjes <rientjes@google.com> Cc: Konstantin Khlebnikov <khlebnikov@openvz.org>, linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>, Oleg Nesterov <oleg@redhat.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Subject: Re: [PATCH] oom: skip frozen tasks Date: Wed, 24 Aug 2011 12:19:27 +0200 [thread overview] Message-ID: <20110824101927.GB3505@tiehlicka.suse.cz> (raw) In-Reply-To: <alpine.DEB.2.00.1108231313520.21637@chino.kir.corp.google.com> On Tue 23-08-11 13:18:14, David Rientjes wrote: > On Tue, 23 Aug 2011, Konstantin Khlebnikov wrote: > > > All frozen tasks are unkillable, and if one of them has TIF_MEMDIE > > we must kill something else to avoid deadlock. After this patch > > select_bad_process() will skip frozen task before checking TIF_MEMDIE. > > > > The caveat is that if the task in the refrigerator is not OOM_DISABLE and > there are no other eligible tasks (system wide, in the cpuset, or in the > memcg) to kill, then the machine will panic as a result of this when, in > the past, we would simply issue the SIGKILL and keep looping in the page > allocator until it is thawed. mem_cgroup_out_of_memory doesn't panic if nothing has been selected. We will loop in the charge&reclaim path until somebody frees some memory. > So you may actually be trading a stall waiting for this thread to thaw for > what would now be a panic, and that's not clearly better to me. When we are in the global OOM condition then you are right, we have a higher chance to panic. I still find the patch an improvement because encountering a frozen task and looping over it without any progress (even though there are other tasks that could be killed) is more probable than having no killable task at all. On non-NUMA machines there is even not a big chance that somebody would be able to thaw a task as the system is already on knees. -- Michal Hocko SUSE Labs SUSE LINUX s.r.o. Lihovarska 1060/12 190 00 Praha 9 Czech Republic -- 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: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2011-08-24 10:19 UTC|newest] Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top 2011-08-23 8:31 [PATCH] oom: skip frozen tasks Konstantin Khlebnikov 2011-08-23 8:31 ` Konstantin Khlebnikov 2011-08-23 9:15 ` KAMEZAWA Hiroyuki 2011-08-23 9:15 ` KAMEZAWA Hiroyuki 2011-08-23 13:46 ` Michal Hocko 2011-08-23 13:46 ` Michal Hocko 2011-08-23 20:18 ` David Rientjes 2011-08-23 20:18 ` David Rientjes 2011-08-24 10:19 ` Michal Hocko [this message] 2011-08-24 10:19 ` Michal Hocko 2011-08-24 19:31 ` David Rientjes 2011-08-24 19:31 ` David Rientjes 2011-08-25 9:19 ` Michal Hocko 2011-08-25 9:19 ` Michal Hocko 2011-08-25 15:18 ` Oleg Nesterov 2011-08-25 15:18 ` Oleg Nesterov 2011-08-25 16:47 ` Michal Hocko 2011-08-25 16:47 ` Michal Hocko 2011-08-25 21:14 ` David Rientjes 2011-08-25 21:14 ` David Rientjes 2011-08-26 7:09 ` Michal Hocko 2011-08-26 7:09 ` Michal Hocko 2011-08-26 8:56 ` Michal Hocko 2011-08-26 8:56 ` Michal Hocko 2011-08-26 9:21 ` David Rientjes 2011-08-26 9:21 ` David Rientjes 2011-08-26 9:53 ` Michal Hocko 2011-08-26 9:53 ` Michal Hocko 2011-08-26 11:01 ` Michal Hocko 2011-08-26 11:01 ` Michal Hocko 2011-08-26 18:13 ` David Rientjes 2011-08-26 18:13 ` David Rientjes 2011-09-26 8:28 ` [PATCH 1/2] oom: do not live lock on " Michal Hocko 2011-09-26 8:28 ` Michal Hocko 2011-09-26 8:56 ` David Rientjes 2011-09-26 8:56 ` David Rientjes 2011-09-26 9:14 ` Michal Hocko 2011-09-26 9:14 ` Michal Hocko 2011-09-26 9:25 ` KAMEZAWA Hiroyuki 2011-09-26 9:25 ` KAMEZAWA Hiroyuki 2011-09-26 9:32 ` Michal Hocko 2011-09-26 9:32 ` Michal Hocko 2011-09-26 15:51 ` Rafael J. Wysocki 2011-09-26 15:51 ` Rafael J. Wysocki 2011-09-26 18:28 ` Michal Hocko 2011-09-26 18:28 ` Michal Hocko 2011-09-27 1:03 ` David Rientjes 2011-09-27 1:03 ` David Rientjes 2011-09-27 7:52 ` Michal Hocko 2011-09-27 7:52 ` Michal Hocko 2011-09-27 18:30 ` David Rientjes 2011-09-27 18:30 ` David Rientjes 2011-09-26 10:28 ` Rusty Russell 2011-09-26 10:28 ` Rusty Russell 2011-09-26 11:05 ` Michal Hocko 2011-09-26 11:05 ` Michal Hocko 2011-09-27 2:21 ` Rusty Russell 2011-09-27 2:21 ` Rusty Russell 2011-09-27 7:03 ` [PATCH] lguest: move process freezing before pending signals check Michal Hocko 2011-09-27 7:03 ` Michal Hocko 2011-09-26 8:35 ` [PATCH 2/2] oom: give bonus to frozen processes Michal Hocko 2011-09-26 8:35 ` Michal Hocko 2011-09-26 9:02 ` David Rientjes 2011-09-26 9:02 ` David Rientjes 2011-09-26 9:31 ` KAMEZAWA Hiroyuki 2011-09-26 9:31 ` KAMEZAWA Hiroyuki 2011-09-26 9:54 ` Michal Hocko 2011-09-26 9:54 ` Michal Hocko 2011-08-26 21:03 ` [PATCH] oom: skip frozen tasks Rafael J. Wysocki 2011-08-26 21:03 ` Rafael J. Wysocki 2011-08-26 10:03 ` Konstantin Khlebnikov 2011-08-26 10:03 ` Konstantin Khlebnikov 2011-08-26 10:48 ` Michal Hocko 2011-08-26 10:48 ` Michal Hocko 2011-08-26 12:44 ` Konstantin Khlebnikov 2011-08-26 12:44 ` Konstantin Khlebnikov 2011-08-26 12:59 ` Michal Hocko 2011-08-26 12:59 ` Michal Hocko 2011-08-26 7:35 ` Konstantin Khlebnikov 2011-08-26 7:35 ` Konstantin Khlebnikov 2011-08-26 9:09 ` David Rientjes 2011-08-26 9:09 ` David Rientjes 2011-08-26 9:59 ` Konstantin Khlebnikov 2011-08-26 9:59 ` Konstantin Khlebnikov 2011-08-26 18:09 ` David Rientjes 2011-08-26 18:09 ` David Rientjes 2011-08-25 21:03 ` Rafael J. Wysocki 2011-08-25 21:03 ` Rafael J. Wysocki
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