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Date:	Wed, 12 Dec 2007 14:28:48 +0100 (CET)
From:	Krzysztof Oledzki <olel@....pl>
To:	bugme-daemon@...zilla.kernel.org
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [Bug 9182] Critical memory leak (dirty pages)



On Tue, 11 Dec 2007, Krzysztof Oledzki wrote:

>
>
> On Wed, 5 Dec 2007, Krzysztof Oledzki wrote:
>
>> 
>> 
>> On Wed, 5 Dec 2007, bugme-daemon@...zilla.kernel.org wrote:
>> 
>>> http://bugzilla.kernel.org/show_bug.cgi?id=9182
>>> 
>>> 
>>> ------- Comment #20 from akpm@...l.org  2007-12-05 13:37 -------
>>> Please monitor the "Dirty:" record in /proc/meminfo.  Is it slowly rising
>>> and never falling?
>> 
>> It is slowly rising with respect to a small fluctuation caused by a current 
>> load.
>> 
>>> Does it then fall if you run /bin/sync?
>> Only a little, by ~1-2MB like in a normal system. But it is not able to 
>> fall below a local minimum. So, after a first sync it does not fall more 
>> with additional synces.
>> 
>>> Compile up usemem.c from
>>> http://www.zip.com.au/~akpm/linux/patches/stuff/ext3-tools.tar.gz and run
>>> 
>>> usemem -m <N>
>>> 
>>> where N is the number of megabytes whcih that machine has.
>> 
>> It has 2GB but:
>> 
>> # ./usemem -m 1662 ; echo $?
>> 0
>> 
>> # ./usemem -m 1663 ; echo $?
>> ./usemem: mmap failed: Cannot allocate memory
>> 1
>>
>>>  Did this cause /proc/meminfo:Dirty to fall?
>> No.
>
> OK, I booted a kernel without 2:2 memsplit but instead with a standard 
> 3.1:0.9 and even without highmem. So, now I have ~900MB and I am able to set 
> -m to the number of megabytes which themachine has. However, usemem still 
> does does not cause dirty memory usage to fall. :(

OK, I can confirm that this is a regression from 2.6.18 where it works OK:

ole@...gar:~$ uname -r
2.6.18.8

ole@...gar:~$ uptime;grep Dirt /proc/meminfo;sync;sleep 2;sync;sleep 1;sync;grep Dirt /proc/meminfo
  14:21:53 up  1:00,  1 user,  load average: 0.23, 0.36, 0.35
Dirty:             376 kB
Dirty:               0 kB

It seems that this leak also exists in my other system as even after many 
synces number of dirty pages are still >> 0, but this the only one where 
it is so critical and at the same time - so easy to reproduce.

Best regards,


 				Krzysztof Olędzki

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