Messages in this thread | | | Subject | Re: VM Problems in 2.6.7 (Too active OOM Killer) | From | Peter Zaitsev <> | Date | Tue, 13 Jul 2004 20:44:02 -0700 |
| |
On Tue, 2004-07-13 at 20:17, Andrea Arcangeli wrote:
> > 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:
Thanks Andrea,
Your reply is very helpful as usually.
> > 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.
When do you think it is going to happen ?
To be honest I recently was quite happy with 2.6.x stability, and in 2.6.7 IO performance for MySQL workloads seems to be mainly fixed - it performs well even with default "as" scheduler. However this problem makes me to be more cautious once again.
> > 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.
The reason for me to disable swap both in 2.4 and 2.6 is - it really hurts performance. In some cases performance can be 2-3 times slower with swap file enabled. Using O_DIRECT and mlock() for buffers helps but not completely.
RedHat 2.4.x kernels are especially affected. They seems to love to get a lot of swap into the swap, however caching the large part of swapped out. This still negatively affects performance.
-- Peter Zaitsev, Senior Support Engineer MySQL AB, www.mysql.com
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |