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SubjectRe: [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@bugzilla.kernel.org wrote:
>>
>>> http://bugzilla.kernel.org/show_bug.cgi?id=9182
>>>
>>>
>>> ------- Comment #20 from akpm@osdl.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@cougar:~$ uname -r
2.6.18.8

ole@cougar:~$ 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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