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From: Balbir Singh <balbir@linux.vnet.ibm.com>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>,
	anfei <anfei.zhou@gmail.com>, Oleg Nesterov <oleg@redhat.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
	nishimura@mxp.nes.nec.co.jp, Mel Gorman <mel@csn.ul.ie>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] oom killer: break from infinite loop
Date: Wed, 31 Mar 2010 12:00:07 +0530	[thread overview]
Message-ID: <20100331063007.GN3308@balbir.in.ibm.com> (raw)
In-Reply-To: <20100331151356.673c16c0.kamezawa.hiroyu@jp.fujitsu.com>

* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2010-03-31 15:13:56]:

> On Tue, 30 Mar 2010 23:07:08 -0700 (PDT)
> David Rientjes <rientjes@google.com> wrote:
> 
> > On Wed, 31 Mar 2010, KAMEZAWA Hiroyuki wrote:
> > 
> > > > > diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> > > > > index 0cb1ca4..9e89a29 100644
> > > > > --- a/mm/oom_kill.c
> > > > > +++ b/mm/oom_kill.c
> > > > > @@ -510,8 +510,10 @@ retry:
> > > > >  	if (PTR_ERR(p) == -1UL)
> > > > >  		goto out;
> > > > >  
> > > > > -	if (!p)
> > > > > -		p = current;
> > > > > +	if (!p) {
> > > > > +		read_unlock(&tasklist_lock);
> > > > > +		panic("Out of memory and no killable processes...\n");
> > > > > +	}
> > > > >  
> > > > >  	if (oom_kill_process(p, gfp_mask, 0, points, limit, mem,
> > > > >  				"Memory cgroup out of memory"))
> > > > > 
> > > > 
> > > > This actually does appear to be necessary but for a different reason: if 
> > > > current is unkillable because it has OOM_DISABLE, for example, then 
> > > > oom_kill_process() will repeatedly fail and mem_cgroup_out_of_memory() 
> > > > will infinitely loop.
> > > > 
> > > > Kame-san?
> > > > 
> > > 
> > > When a memcg goes into OOM and it only has unkillable processes (OOM_DISABLE),
> > > we can do nothing. (we can't panic because container's death != system death.)
> > > 
> > > Because memcg itself has mutex+waitqueue for mutual execusion of OOM killer, 
> > > I think infinite-loop will not be critical probelm for the whole system.
> > > 
> > > And, now, memcg has oom-kill-disable + oom-kill-notifier features.
> > > So, If a memcg goes into OOM and there is no killable process, but oom-kill is
> > > not disabled by memcg.....it means system admin's mis-configuraton.
> > > 
> > > He can stop inifite loop by hand, anyway.
> > > # echo 1 > ..../group_A/memory.oom_control
> > > 
> > 
> > Then we should be able to do this since current is by definition 
> > unkillable since it was not found in select_bad_process(), right?
> 
> To me, this patch is acceptable and seems reasnoable.
> 
> But I didn't joined to memcg development when this check was added
> and don't know why kill current..
>

The reason for adding current was that we did not want to loop
forever, since it stops forward progress - no error/no forward
progress. It made sense to oom kill the current process, so that the
cgroup admin could look at what went wrong.
 
> http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c7ba5c9e8176704bfac0729875fa62798037584d
> 
> Addinc Balbir to CC. Maybe situation is changed now.
> Because we can stop inifinite loop (by hand) and there is no rushing oom-kill
> callers, this change is acceptable.
>

By hand is not always possible if we have a large number of cgroups
(I've seen a setup with 2000 cgroups on libcgroup ML). 2000 cgroups *
number of processes make the situation complex. I think using OOM
notifier is now another way of handling such a situation.
 
-- 
	Three Cheers,
	Balbir

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  reply	other threads:[~2010-03-31  6:30 UTC|newest]

Thread overview: 115+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-03-24 16:25 [PATCH] oom killer: break from infinite loop Anfei Zhou
2010-03-25  2:51 ` KOSAKI Motohiro
2010-03-26 22:08 ` Andrew Morton
2010-03-26 22:33   ` Oleg Nesterov
2010-03-28 14:55     ` anfei
2010-03-28 16:28       ` Oleg Nesterov
2010-03-28 21:21         ` David Rientjes
2010-03-29 11:21           ` Oleg Nesterov
2010-03-29 20:49             ` [patch] oom: give current access to memory reserves if it has been killed David Rientjes
2010-03-30 15:46               ` Oleg Nesterov
2010-03-30 20:26                 ` David Rientjes
2010-03-31 17:58                   ` Oleg Nesterov
2010-03-31 20:47                     ` Oleg Nesterov
2010-04-01  8:35                       ` David Rientjes
2010-04-01  8:57                         ` [patch -mm] oom: hold tasklist_lock when dumping tasks David Rientjes
2010-04-01 14:27                           ` Oleg Nesterov
2010-04-01 19:16                             ` David Rientjes
2010-04-01 13:59                         ` [patch] oom: give current access to memory reserves if it has been killed Oleg Nesterov
2010-04-01 19:12                           ` David Rientjes
2010-04-02 11:14                             ` Oleg Nesterov
2010-04-02 18:30                               ` [PATCH -mm 0/4] oom: linux has threads Oleg Nesterov
2010-04-02 18:31                                 ` [PATCH -mm 1/4] oom: select_bad_process: check PF_KTHREAD instead of !mm to skip kthreads Oleg Nesterov
2010-04-02 19:05                                   ` David Rientjes
2010-04-02 18:32                                 ` [PATCH -mm 2/4] oom: select_bad_process: PF_EXITING check should take ->mm into account Oleg Nesterov
2010-04-06 11:42                                   ` anfei
2010-04-06 12:18                                     ` Oleg Nesterov
2010-04-06 13:05                                       ` anfei
2010-04-06 13:38                                         ` Oleg Nesterov
2010-04-02 18:32                                 ` [PATCH -mm 3/4] oom: introduce find_lock_task_mm() to fix !mm false positives Oleg Nesterov
2010-04-02 18:33                                 ` [PATCH -mm 4/4] oom: oom_forkbomb_penalty: move thread_group_cputime() out of task_lock() Oleg Nesterov
2010-04-02 19:04                                   ` David Rientjes
2010-04-05 14:23                                 ` [PATCH -mm] oom: select_bad_process: never choose tasks with badness == 0 Oleg Nesterov
2010-04-02 19:02                               ` [patch] oom: give current access to memory reserves if it has been killed David Rientjes
2010-04-02 19:14                                 ` Oleg Nesterov
2010-04-02 19:46                                   ` David Rientjes
2010-04-02 19:54                                     ` [patch -mm] oom: exclude tasks with badness score of 0 from being selected David Rientjes
2010-04-02 21:04                                       ` Oleg Nesterov
2010-04-02 21:22                                         ` [patch -mm v2] " David Rientjes
2010-04-02 20:55                                     ` [patch] oom: give current access to memory reserves if it has been killed Oleg Nesterov
2010-03-31 21:07                     ` David Rientjes
2010-03-31 22:50                       ` Oleg Nesterov
2010-03-31 23:30                         ` Oleg Nesterov
2010-03-31 23:48                           ` David Rientjes
2010-04-01 14:39                             ` Oleg Nesterov
2010-04-01 18:58                               ` David Rientjes
2010-04-01  8:25                         ` David Rientjes
2010-04-01 15:26                           ` Oleg Nesterov
2010-04-08 21:08                             ` David Rientjes
2010-04-09 12:38                               ` Oleg Nesterov
2010-03-30 16:39               ` [PATCH] oom: fix the unsafe proc_oom_score()->badness() call Oleg Nesterov
2010-03-30 17:43                 ` [PATCH -mm] proc: don't take ->siglock for /proc/pid/oom_adj Oleg Nesterov
2010-03-30 20:30                   ` David Rientjes
2010-03-31  9:17                     ` Oleg Nesterov
2010-03-31 18:59                     ` Oleg Nesterov
2010-03-31 21:14                       ` David Rientjes
2010-03-31 23:00                         ` Oleg Nesterov
2010-04-01  8:32                           ` David Rientjes
2010-04-01 15:37                             ` Oleg Nesterov
2010-04-01 19:04                               ` David Rientjes
2010-03-30 20:32                 ` [PATCH] oom: fix the unsafe proc_oom_score()->badness() call David Rientjes
2010-03-31  9:16                   ` Oleg Nesterov
2010-03-31 20:17                     ` Oleg Nesterov
2010-04-01  7:41                       ` David Rientjes
2010-04-01 13:13                         ` [PATCH 0/1] oom: fix the unsafe usage of badness() in proc_oom_score() Oleg Nesterov
2010-04-01 13:13                           ` [PATCH 1/1] " Oleg Nesterov
2010-04-01 19:03                             ` David Rientjes
2010-03-29 14:06           ` [PATCH] oom killer: break from infinite loop anfei
2010-03-29 20:01             ` David Rientjes
2010-03-30 14:29               ` anfei
2010-03-30 20:29                 ` David Rientjes
2010-03-31  0:57                   ` KAMEZAWA Hiroyuki
2010-03-31  6:07                     ` David Rientjes
2010-03-31  6:13                       ` KAMEZAWA Hiroyuki
2010-03-31  6:30                         ` Balbir Singh [this message]
2010-03-31  6:31                           ` KAMEZAWA Hiroyuki
2010-03-31  7:04                             ` David Rientjes
2010-03-31  6:32                           ` David Rientjes
2010-03-31  7:08                             ` [patch -mm] memcg: make oom killer a no-op when no killable task can be found David Rientjes
2010-03-31  7:08                               ` KAMEZAWA Hiroyuki
2010-03-31  8:04                               ` Balbir Singh
2010-03-31 10:38                                 ` David Rientjes
2010-04-04 23:28                               ` David Rientjes
2010-04-05 21:30                                 ` Andrew Morton
2010-04-05 22:40                                   ` David Rientjes
2010-04-05 22:49                                     ` Andrew Morton
2010-04-05 23:01                                       ` David Rientjes
2010-04-06 12:08                                         ` KOSAKI Motohiro
2010-04-06 21:47                                           ` David Rientjes
2010-04-07  0:20                                             ` KAMEZAWA Hiroyuki
2010-04-07 13:29                                               ` KOSAKI Motohiro
2010-04-08 18:05                                                 ` David Rientjes
2010-04-21 19:17                                                   ` Andrew Morton
2010-04-21 22:04                                                     ` David Rientjes
2010-04-22  0:23                                                       ` KAMEZAWA Hiroyuki
2010-04-22  8:34                                                         ` David Rientjes
2010-04-27 22:58                                                       ` [patch -mm] oom: reintroduce and deprecate oom_kill_allocating_task David Rientjes
2010-04-28  0:57                                                         ` KAMEZAWA Hiroyuki
2010-04-22  7:23                                                     ` [patch -mm] memcg: make oom killer a no-op when no killable task can be found Nick Piggin
2010-04-22  7:25                                                       ` KAMEZAWA Hiroyuki
2010-04-22 10:09                                                         ` Nick Piggin
2010-04-22 10:27                                                           ` KAMEZAWA Hiroyuki
2010-04-22 21:11                                                             ` David Rientjes
2010-04-22 10:28                                                           ` David Rientjes
2010-04-22 15:39                                                             ` Nick Piggin
2010-04-22 21:09                                                               ` David Rientjes
2010-05-04 23:55                                                     ` David Rientjes
2010-04-08 17:36                                               ` David Rientjes
2010-04-02 10:17           ` [PATCH] oom killer: break from infinite loop Mel Gorman
2010-04-04 23:26             ` David Rientjes
2010-04-05 10:47               ` Mel Gorman
2010-04-06 22:40                 ` David Rientjes
2010-03-29 11:31         ` anfei
2010-03-29 11:46           ` Oleg Nesterov
2010-03-29 12:09             ` anfei
2010-03-28  2:46 ` David Rientjes

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