Re: VM Problems in 2.6.7 (Too active OOM Killer)

[Andrea Arcangeli <andrea@suse.de>]

Hello Peter,

On Tue, Jul 13, 2004 at 07:23:44PM -0700, Peter Zaitsev wrote:
> Hi,
> 
> To be honest I was truly surprised seeing OOM killer killing MySQL
> without any good reason during highly IO intensive test:
> 
> Out of Memory: Killed process 19301 (mysqld).
> Out of Memory: Killed process 19302 (mysqld).
> Out of Memory: Killed process 19303 (mysqld).
> Out of Memory: Killed process 19304 (mysqld).
> Out of Memory: Killed process 19305 (mysqld).
> Out of Memory: Killed process 19306 (mysqld).
> Out of Memory: Killed process 19309 (mysqld).
> Out of Memory: Killed process 19310 (mysqld).
> Out of Memory: Killed process 19311 (mysqld).
> Out of Memory: Killed process 19312 (mysqld).
> Out of Memory: Killed process 19737 (mysqld).
> Out of Memory: Killed process 19739 (mysqld).
> Out of Memory: Killed process 19821 (mysqld).

this is a well known 2.6 oom-killer problem w/o swap. Not the worst one,
I mentioned the worst one here just a few weeks ago:
	
	http://groups.google.com/groups?q=g:thl1518647992d&dq=&hl=en&lr=&ie=UTF-8&selm=fa.i50b3kk.p0qsjs%40ifi.uio.no


the only fix at the moment is to use 2.4 with oom killer disabled (the
same issue could happen with 2.4 too). even if it would work better than
the above the oom killer will still get screwed by mlock and it simply
cannot know how much lowmem is freeable leading to deadlock instead of
-ENOMEM with syscalls if you fill the whole lowmem zone.

I fixed everything related to oom in 2.4 some year back, now need to
port to 2.6.

workaround is to add swap in 2.6, but in some condition it'll still
underpeform compared to 2.4 due the lack of the zone-reserve-ratio algo.