From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: David Rientjes <rientjes@google.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>, Nick Piggin <npiggin@suse.de>,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
linux-mm@kvack.org
Subject: Re: [patch -mm v2 04/10] oom: remove special handling for pagefault ooms
Date: Wed, 3 Mar 2010 09:44:38 +0900 [thread overview]
Message-ID: <20100303094438.1e9b09fb.kamezawa.hiroyu@jp.fujitsu.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1003021634030.18535@chino.kir.corp.google.com>
On Tue, 2 Mar 2010 16:38:16 -0800 (PST)
David Rientjes <rientjes@google.com> wrote:
> On Wed, 3 Mar 2010, KAMEZAWA Hiroyuki wrote:
>
> > > This patch causes a regression??? You never said that in any of your
> > > reviews and I have no idea what you're talking about, this patch simply
> > > cleans up the code and closes a race where VM_FAULT_OOM could needlessly
> > > kill tasks in parallel oom conditions.
> > >
> > try_set_system_oom() is not called in memory_cgroup_out_of_memory() path.
> > Then, oom kill twice.
> >
>
> So how does this cause a regression AT ALL? Calling try_set_system_oom()
> in pagefault_out_of_memory() protects against concurrent out_of_memory()
> from the page allocator before a task is actually killed. So this patch
> closes that race entirely. So it most certainly does not introduce a
> regression.
>
> You said earlier that mem_cgroup_out_of_memory() need not serialize
> against parallel oom killings because in that scenario we must kill
> something anyway, memory freeing from other ooms won't help if a memcg is
> over its limit. So, yeah, we may kill two tasks if both the system and a
> memcg are oom in parallel and neither have actually killed a task yet, but
> that's much more jusitiable since we shouldn't rely on a memcg oom to free
> memory for the entire system.
>
> So, again, there's absolutely no regression introduced by this patch.
>
I'm sorry if I miss somthing.
memory_cgroup_out_of_memory() kills a task. and return VM_FAULT_OOM then,
page_fault_out_of_memory() kills another task.
and cause panic if panic_on_oom=1.
Then, if we remove mem_cgroup_oom_called(), we have to take care that
memcg doesn't cause VM_FAULT_OOM.
Thanks,
-Kame
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next prev parent reply other threads:[~2010-03-03 0:48 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-26 23:52 [patch -mm v2 00/10] oom killer rewrite David Rientjes
2010-02-26 23:53 ` [patch -mm v2 01/10] oom: filter tasks not sharing the same cpuset David Rientjes
2010-03-02 4:54 ` Balbir Singh
2010-02-26 23:53 ` [patch -mm v2 02/10] oom: sacrifice child with highest badness score for parent David Rientjes
2010-03-02 4:54 ` Balbir Singh
2010-02-26 23:53 ` [patch -mm v2 03/10] oom: select task from tasklist for mempolicy ooms David Rientjes
2010-02-26 23:53 ` [patch -mm v2 04/10] oom: remove special handling for pagefault ooms David Rientjes
2010-03-01 1:12 ` KAMEZAWA Hiroyuki
2010-03-01 10:13 ` David Rientjes
2010-03-01 23:59 ` KAMEZAWA Hiroyuki
2010-03-02 23:55 ` David Rientjes
2010-03-03 0:24 ` KAMEZAWA Hiroyuki
2010-03-03 0:44 ` David Rientjes
2010-03-01 5:23 ` Balbir Singh
2010-03-01 10:04 ` David Rientjes
2010-03-01 23:55 ` KAMEZAWA Hiroyuki
2010-03-03 0:01 ` David Rientjes
2010-03-03 0:22 ` KAMEZAWA Hiroyuki
2010-03-03 0:38 ` David Rientjes
2010-03-03 0:44 ` KAMEZAWA Hiroyuki [this message]
2010-03-03 0:53 ` David Rientjes
2010-03-03 0:58 ` KAMEZAWA Hiroyuki
2010-03-03 23:27 ` David Rientjes
2010-03-04 3:59 ` KAMEZAWA Hiroyuki
2010-03-04 6:50 ` David Rientjes
2010-03-04 7:00 ` KAMEZAWA Hiroyuki
2010-03-04 9:50 ` David Rientjes
2010-03-05 0:58 ` KAMEZAWA Hiroyuki
2010-03-02 2:21 ` KAMEZAWA Hiroyuki
2010-03-02 23:59 ` David Rientjes
2010-02-26 23:53 ` [patch -mm v2 05/10] oom: badness heuristic rewrite David Rientjes
2010-02-26 23:53 ` [patch -mm v2 06/10] oom: deprecate oom_adj tunable David Rientjes
2010-02-26 23:53 ` [patch -mm v2 07/10] oom: replace sysctls with quick mode David Rientjes
2010-02-26 23:53 ` [patch -mm v2 08/10] oom: avoid oom killer for lowmem allocations David Rientjes
2010-02-26 23:53 ` [patch -mm v2 09/10] oom: remove unnecessary code and cleanup David Rientjes
2010-02-26 23:53 ` [patch -mm v2 10/10] oom: default to killing current for pagefault ooms David Rientjes
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