OOM killer "Out of Memory: Killed process" SOLUTIONS / SUMMARY

[Eric Sisler]

On Fri, 2007-08-17 at 17:34 -0400, Cristian Silva wrote:

> This is great info.
> 
> We are having this problem on a RHEL5 server with 8gb of ram (32bits) since
> some time ago.
> 
> I understand that the hugemem kernel is no longer available in RHEL5, so we
> installed the PAE kernel but it makes no difference, we still have the oom.

Does the PAE kernel report a different amount of total low memory than
the regular kernel?  If not, are there BIOS or boot time options that
might help?  From a post to the RHEL4 list by Tom Sightler:

Because of the way Redhat has reworked the kernels included in RHEL5 it
shouldn't really have this issue.  For the 32-bit version of RHEL5 there
are really only two kernel (not counting the xen kernel).  You can have
either the standard kernel or the PAE kernel, but according to the
release notes the standard kernel is limited to recognizing 4GB (I have
not verified this) so if you have more memory than that you have to use
the PAE kernel.  The PAE kernel is basically the RHEL5 equivalent to the
hugemem kernel in previous releases so effectively Redhat no longer
gives you the option to run a non-hugemem kernel on systems with more
than 4GB of RAM.  That should effectively be the same as RHEL4 running
the hugemem kernel which usually effectively prevents this issue.

For a more accurate and detailed description of the problems involved
some people might want to read the following article:

http://kerneltrap.org/node/2450 "

How close to 8Gb are you with virtual machines?  Perhaps you really are
running out of memory...?

> 64bits is not an option at the moment, so if i understand correctly, using
> just 4gb of ram instead of the 8gb that we currently have, could potentially
> solve the oom-killer problem ?

You might be able to get away with ~6Gb.  I'd try the
vm.lower_zone_protection first, followed by other kernel options
suggested by Ray (and others).

-Eric

-- 
Eric Sisler <esisler at westminster.lib.co.us>
Library Network Specialist
Westminster Public Library
Westminster, CO USA

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