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

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Message-ID: <CAP145piK2kW4F94pNdKpo_sGg8OD914exOtwCx2o+83jx5Toog@mail.gmail.com>
Date:	Mon, 7 May 2012 23:41:51 +0200
From:	Robert Święcki <robert@...ecki.net>
To:	Christoph Lameter <cl@...ux.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: mmap/clone returns ENOMEM with lots of free memory

On Mon, May 7, 2012 at 10:15 PM, Christoph Lameter <cl@...ux.com> wrote:
> On Mon, 7 May 2012, Robert Święcki wrote:
>
>> root@...-test:~/kern-fuz# ./cont.sh
>> su: Cannot fork user shell
>> su: Cannot fork user shell
>> su: Cannot fork user shell
>>
>> root@...-test:~/kern-fuz# strace -e mmap,clone su test -c 'kill -CONT
>> -1' 2>&1 | grep "= \-1"
>> clone(child_stack=0,
>> flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
>> child_tidptr=0x7fadf334f9f0) = -1 ENOMEM (Cannot allocate memory)
>> mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1,
>> 0) = -1 ENOMEM (Cannot allocate memory)
>
> Hmmm... That looks like some maximum virtual memory limit was violated.
>
> Check ulimit and the overcommit settings (see /proc/meminfo's commitlimit
> etc)

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

root@...-test:/proc# grep Mem /proc/meminfo
MemTotal:        3963060 kB
MemFree:         3098324 kB

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

-- 
Robert Święcki
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