Re: [Bug 9182] Critical memory leak (dirty pages)

[Krzysztof Oledzki <olel@ans.pl>]

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