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

["J. Bruce Fields" <bfields@fieldses.org>]

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