linux-kernel - Re: mmap/clone returns ENOMEM with lots of free memory

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Message-ID: <alpine.DEB.2.00.1205080859570.25669@router.home>
Date:	Tue, 8 May 2012 09:02:46 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Robert Święcki <robert@...ecki.net>
cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: mmap/clone returns ENOMEM with lots of free memory

On Mon, 7 May 2012, Robert Święcki wrote:

> Yup (btw: I attached dump of some proc files and some debug commands
> in the original e-mail - can be found here
> http://marc.info/?l=linux-kernel&m=133640623421007&w=2 in case some
> MTA removed them)
>
> CommitLimit:     1981528 kB
> Committed_AS:    1916788 kB
>
> just not sure if Committed_AS should present this kind of value. Did I
> just hit a legitimate condition, or may it suggest a bug? I'm a bit
> puzzled cause

This is a legitimate condition. No bug.
>
> root@...-test:/proc# grep Mem /proc/meminfo
> MemTotal:        3963060 kB
> MemFree:         3098324 kB

Physical memory is free in quantity but virtual memory is exhausted.

> Also, some sysctl values:
> vm.overcommit_memory = 2
> vm.overcommit_ratio = 50

Setting overcommit memory to 2 means that the app is strictly policed
for staying within bounds on virtual memory. Dont do that.

See linux source linux/Documentation/vm/overcommit-accounting for more
details.