[Ocfs2-users] out of memory... doing heavy IO on ocfs2 is wasting (low) memory?!

[Kurt Hackel]

Hi,

Alexander Finger wrote:
> Hello,
>
> my problem: When I want to create a large number of small files on any 
> node at my ocfs2 cluster, after some time the oom killer starts 
> killing processes because of low LowMem. All error messages and memory 
> stats are at the end of this mail.

This is a known issue that is being currently fixed for the next 
scheduled release.  At this time, once a node masters a lock resource 
(from the filesystem this would happen if the node were the first node 
to access that file) it cannot drop the mastery of that resource until 
it unmounts.  The fix is nontrivial but I'm almost done with it.  Once 
the fix is done it will need extensive testing.

> The only way to avoid this behavoir is to unmount the ocfs2 partition 
> after some disk operations, because LowMem (LowFree) stays low until 
> unmount... I searched the web and found many descriptions of this 
> error, but no answer how to handle this problem.
Correct.  The only current workaround is to unmount, or to attempt to 
spread the lock resources out across all the nodes of the cluster (which 
may be impossible in your usage case).

Thanks
-kurt