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

[Andrew Morton <akpm@osdl.org>]

Peter Zaitsev <peter@mysql.com> wrote:
>
> > 
> > wrt this OOM problem: it's possible that your ZONE_NORMAL got filled with
> > anonymous memory which the VM is unable to do anything about.  If you're
> > going to run a highmem box swapless then you should tune the kernel so that
> > it doesn't use so much ZONE_NORMAL memory for anonymous pages.
> 
> My concern is mainly users which normally run kernel with default
> settings. Things should work for them as well. 

Yes, it could be that the default value of zero for lower_zone_protection
is not appropriate.

> To be honest I do not really understand this OOM without swap problem at
> all, why is it possible to move pages from ZONE_NORMAL to swap but not
> to other zones ? 

If the kernel has no swap there is nothing it can do with an anonymous page
(ie: the thing whcih malloc() gives you).  It is effectively pinned memory,
because there's nowhere we can write it to get rid of it.

If you end up pinning all of your ZONE_NORMAL pages with anonymous memory,
further GFP_KERNEL allocation attempts will go oom.