linux-kernel - Re: v3.4-rc2 out-of-memory problems (was Re: 3.4-rc1 sticks-and-crashs)

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Message-ID: <4F831A5E.3040907@redhat.com>
Date:	Mon, 09 Apr 2012 13:20:30 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Sven Joachim <svenjoac@....de>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	werner <w.landgraf@...ru>, David Rientjes <rientjes@...gle.com>,
	Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
	Oleg Nesterov <oleg@...hat.com>
Subject: Re: v3.4-rc2 out-of-memory problems (was Re: 3.4-rc1 sticks-and-crashs)

On 04/09/2012 01:00 PM, Sven Joachim wrote:
> On 2012-04-09 18:33 +0200, Rik van Riel wrote:
>
>> On 04/09/2012 12:19 PM, Sven Joachim wrote:
>>> On 2012-04-09 17:57 +0200, Rik van Riel wrote:
>>>
>>>> On 04/09/2012 03:04 AM, Sven Joachim wrote:
>>>>
>>>>> While I did not experience any crashes or instabilities (yet?), I'm also
>>>>> seeing memory leaks.  On a system started this morning, with hardly
>>>>> anything running:
>>>>
>>>>> where I would expect no more than 50 MB used, 400 MB are actually in use:
>>>>>
>>>>> ,----
>>>>> | $ free
>>>>> |              total       used       free     shared    buffers     cached
>>>>> | Mem:       3348400    1849712    1498688          0     328960    1119180
>>>>> | -/+ buffers/cache:     401572    2946828
>>>>> | Swap:      3719040          0    3719040
>>>>> `----
>>>>
>>>> Do you see any big memory users in /proc/meminfo or in
>>>> /proc/slabinfo?
>>>
>>> Attaching these files, since I can't really make anything out of the
>>> latter.  Note that I started a few memory hogs (X, Firefox, Emacs with
>>> Gnus), so overall memory footprint has grown to 768 MB.
>>
>> Looks like the "missing" 400MB is all in filesystem caches,
>> specifically the dentry cache, the ext4 inode cache and
>> buffer heads.
>
> Then why does free(1) report those in the "-/+ buffers/cache:" line?  It
> did not do this with earlier kernels, AFAIK.

It has done so for over a decade. Reclaimable slab has never been
subtracted from "used" by the free utility.

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