[Xen-users] Re: oom-killer keeps killing big un-tars

[Stephan Seitz <nur-ab-sal@xxxxxx>]

On Wed, May 18, 2005 at 11:43:36AM -0400, Andrew Thompson wrote:
> Several times now, I've been untarring some files in my dom0 and they've 
> been killed by the oom-killer. I originally thought it might be because 
Hm, can you reproduce this with kernel 2.6.7?

Without using xen I hit the same bug. The oom-killer was changed in
2.6.8 IIRC. On a "normal" pc with 512 MB RAM (and lots of swap) I
could hit the oom-killer creating a big tar archive (> 60GB
uncompressed) or even running samba3 and apache2 (for subversion).
Free and top didn't show any signs for running out of memory.
So 2.6.8 and 2.6.9 were quite unusable for me. In the newer kernels
the oom-killer seems to be not so aggressive anymore (at least on my
system). Google shows, that you can tweak your vm settings with
sysctl.

Back to xen:
When I wanted to test xen I tried to build a new SuSE domain. Dom0 was
running Debian as well as another domain. Both didn't have much to do.
Since SuSE seems to lack a brilliant tool like debootstrap, I copied
an existing SuSE installation to an image file, transfered the image to
Dom0, mounted it via loopback and tried to copy the files to a new
partition (reiserfs). With not much success, because the oom-killer
was getting reproducable in my way (killing sometimes the copy
process, sometimes the sshd). When I doubled the memory for Dom0 (I
think from 64 to 128 MB), the oom-killer stopped.
So it seems, for new kernels, you need a lot of RAM for some
operations, even if top or free reporting enough free memory.
Maybe it has to do with mount options for reiserfs, which was the
target fs for all oom-killer actions.

You seem to have reiserfs, too. Could you mount it with data=writeback
and try again? This is the fastest (and in some way unsafest) option.
Your write performance will increase very much. I'm normally using
data=journal, the safest and slowest option.
Maybe some other guys can tell, if journalling code is unswappable and
can lead to oom-killer.

Shade and sweet water!

        Stephan

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| Stephan Seitz                    E-Mail: Nur-Ab-Sal@xxxxxx |
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