Re: High load in 2.6.27, NFS / rpcauth_lookup_credcache()?

J. Bruce Fields
2008-10-22T17:56:29Z

On Wed, Oct 22, 2008 at 11:12:08AM +0200, Max Kellermann wrote:
> Hi,
>
> after I was able to fix http://lkml.org/lkml/2008/10/17/147, the
> server which was already upgraded to 2.6.27.2 still gets very high
> load. It is a web server with NFS file storage (NetApp), and while
> the others in the cluster (kernel 2.6.25) have a load of 1-3, 2.6.27.2
> gets 30-50.
>
> I did an oprofile, with the following results (server just started,
> load "only" 5-10):

Well, there's only 7 patches to net/sunrpc/auth.c between 2.6.25 and
today, so worst case a 'git bisect v2.6.25..v2.6.27 net/sunrpc/auth.c'
might not be too bad.

No particular idea why rpcauth_lookup_credcache would be a problem,
though.

--b.

>
> 87593 56.1116 (no location information) vmlinux
> vmlinux rpcauth_lookup_credcache
> 16037 10.2732 auth_generic.c:0 vmlinux
> vmlinux generic_match
> 6460 4.1382 (no location information) php4
> php4 (no symbols)
> 2478 1.5874 (no location information) libc-2.7.so
> libc-2.7.so (no symbols)
> [...]
>
> We havn't configured any special authentication method. It is a NFSv3
> over UDP mount, but the kernel has NFSv4 and therefore KRB5 enabled.
>
> Any ideas why rpcauth_lookup_credcache() goes overboard with CPU
> usage?
>
> Max