linux-kernel - Re: [PATCH for 3.2.34] memcg: do not trigger OOM from add_to_page_cache

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Message-ID: <20121130161923.GN29317@dhcp22.suse.cz>
Date:	Fri, 30 Nov 2012 17:19:23 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	azurIt <azurit@...ox.sk>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	cgroups mailinglist <cgroups@...r.kernel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH for 3.2.34] memcg: do not trigger OOM from
 add_to_page_cache_locked

On Fri 30-11-12 16:59:37, azurIt wrote:
> >> Here is the full boot log:
> >> www.watchdog.sk/lkml/kern.log
> >
> >The log is not complete. Could you paste the comple dmesg output? Or
> >even better, do you have logs from the previous run?
> 
> 
> What is missing there? All kernel messages are logging into
> /var/log/kern.log (it's the same as dmesg), dmesg itself was already
> rewrited by other messages. I think it's all what that kernel printed.

Early boot messages are missing - so exactly the BIOS memory map I was
asking for. As the NUMA has been excluded it is probably not that
relevant anymore.
The important question is why you see VM_FAULT_OOM and whether memcg
charging failure can trigger that. I don not see how this could happen
right now because __GFP_NORETRY is not used for user pages (except for
THP which disable memcg OOM already), file backed page faults (aka
__do_fault) use mem_cgroup_newpage_charge which doesn't disable OOM.
This is a real head scratcher.

Could you also post your complete containers configuration, maybe there
is something strange in there (basically grep . -r YOUR_CGROUP_MNT
except for tasks files which are of no use right now).
-- 
Michal Hocko
SUSE Labs
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