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

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Date:	Fri, 30 Nov 2012 15:44:31 +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 14:44:27, azurIt wrote:
> >Anyway your system is under both global and local memory pressure. You
> >didn't see apache going down previously because it was probably the one
> >which was stuck and could be killed.
> >Anyway you need to setup your system more carefully.
> 
> 
> There is, also, an evidence that system has enough of memory! :) Just
> take column 'rss' from process list in OOM message and sum it - you
> will get 2489911. It's probably in KB so it's about 2.4 GB. System has
> 14 GB of RAM so this also match data on my graph - 2.4 is about 17% of
> 14.

Hmm, that corresponds to the ZONE_DMA32 size pretty nicely but that zone
is hardly touched:
Nov 30 02:53:56 server01 kernel: [  818.241291] DMA32 free:2523636kB min:2672kB low:3340kB high:4008kB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:2542248kB mlocked:0kB dirty:0kB writeback:0kB mapped:4kB shmem:0kB slab_reclaimable:0kB slab_unreclaimable:0kB kernel_stack:0kB pagetables:0kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no

DMA32 zone is usually fills up first 4G unless your HW remaps the rest
of the memory above 4G or you have a numa machine and the rest of the
memory is at other node. Could you post your memory map printed during
the boot? (e820: BIOS-provided physical RAM map: and following lines)

There is also ZONE_NORMAL which is also not used much
Nov 30 02:53:56 server01 kernel: [  818.242163] Normal free:6924716kB min:12512kB low:15640kB high:18768kB active_anon:1463128kB inactive_anon:2072kB active_file:1803964kB inactive_file:1072628kB unevictable:3924kB isolated(anon):0kB isolated(file):0kB present:11893760kB mlocked:3924kB dirty:1000kB writeback:776kB mapped:35656kB shmem:3828kB slab_reclaimable:202560kB slab_unreclaimable:50696kB kernel_stack:2944kB pagetables:158616kB unstable:0kB bounce:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no

You have mentioned that you are comounting with cpuset. If this happens
to be a NUMA machine have you made the access to all nodes available?
Also what does /proc/sys/vm/zone_reclaim_mode says?
-- 
Michal Hocko
SUSE Labs
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