rpc.mountd at 99% cpu

[Brian Elliott Finley <finley@anl.gov>]

I've got an nfs server (quad cpu amd64, 36G mem, failover fiberchannel)
running ubuntu, and I'm getting the following behavior that I haven't
been able to track down yet:

    * rpc.mountd spikes to 99% cpu usage when a client machine mounts,
      causing a temporary disruption in service to all client systems

Google, NFS Howtos, NFS Perf Tuning docs, IRC (can't find an NFS
specific IRC channel), local sysadmins all turn up nothing so far.  Here
are potentially relavant data:

    * exportfs -v -o rw,secure,sync,no_root_squash
      10.10.0.0/255.255.0.0:/export/home
    * nfs server has all clients info in /etc/hosts
    * /etc/hosts is first in nsswitch.conf
    * kernel is ubuntu's: linux-image-2.6.10-5-amd64-k8-smp
    * nfs performance is fine once a filesystem is mounted
    * unless, someone else is mounting a filesystem, in which case
      already mounted filesystems
    * only 8 clients
    * home directories mounted by autofs on clients as
      server:/export/home/bob /home/bob
    * 32 nfsd threads
    * % netstat -in
      Kernel Interface table
      Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR   TX-OK TX-ERR TX-DRP
      TX-OVR Flg
      eth0   1500 0  247854230      0      0      0324570001      0
      0      0 BMRU
      eth1   1500 0  1022171197      0      0      0258643880
      0      0      0 BMR U
      lo    16436 0    419024      0      0      0  419024      0
      0      0 LRU
    * % cat /proc/net/rpc/nfsd | grep ^th
      th 32 8229 13759.142 6537.314 1919.479 4.212 129.977 52.636 11.780
      10.231 0.000 101.321
    * caching bind9 installed on server, and it points to itself for
      first nameserver entry

Any one know what's up here?  Or how I can tell what's making rpc.mountd
take so much time?

-- 
Brian Elliott Finley
Linux Strategist, CIS
Desk: 630.252.4742
Cell: 630.631.6621



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