Re: What's the NFS OOM problem?

[Willy Tarreau <w@1wt.eu>]

On Tue, Aug 08, 2006 at 06:24:47PM -0400, Xin Zhao wrote:
> I often heard of the OOM probelm in NFS, but don't know what it is.
> Now I am developing a NFS based system and found my system memory
> (server side) is used too fast. I checked the code but didn't find
> memory leaking. So I suspect I run into OOM issue.

I simply think that you're cache is filling while your clients access
a lot of files. That's expected. You might also get quite a bunch of
dentries cached which will not be accounted for in meminfo. Check
/proc/meminfo for the cache+buffer size, and check /proc/slabinfo for
the number of dentries. The usual way to ensure this is only cache is
to allocate a large amount of memory (let's say all the system RAM
provided that everything can get swapped), then free it. You'll see
a lot of free memory after that.

> Can someone help me and give me a brief description on OOM issue?

I don't know about any OOM issue related to NFS. At most it might happen
on the client (eg: stating firefox from an NFS root) which might not have
enough memory for new network buffers, but I don't even know if it's
possible at all.

Regards,
Willy