nfs-kernel-server: high cpu load (100% for 20-40 seconds, every mount)

[H.-Dirk Schmitt]

Package: nfs-kernel-server
Version: 1:1.0.12-4
Severity: important



Every mount of a nfs share from a client computer have as result a
mentionable wait time on the client and rpc.mountd consuming nearly 100% cpu
time for 20-40 seconds. After that time, it works o.k. till the next mount
request.

This behavior is all newer nfs-kernel-server packages.
In the current state the package is not usable for nfs-server with more as
occasional mounts. 

The problem also arise on a similar machine - the main nfs server.
(Both with opteron cpu, 2 Gb RAM, scsi disks, and also a sata raid on the
main nfs server). 

Here I have 4 client computers mounting resources from the nfs-server via
automouunt. To avoid the problem I revert nfs-kernel-server package to 
1.0.9-2ubuntu1 on the production nfs-server. This version hasn't this bug.  

If I upgrade the nfs-kernel-server on the production nfs-server the cpu load
rise to 100% for 3 minutes. After a period of time the high cpu load occurs
again for several minutes.
During the period of high cpu load other mount request are failing.
syslog: "Oct 21 19:42:14 donald automount[16634]: >> mount to NFS server 'garfield'
         failed."


I also tested the behavior in gutsy in to ways.
1.) Partial upgrade of a feisty machine with guty nfs-kernel-server and
depended packages.
2.) Clean gutsy machine (release upgraded from feisty installation)

The high load for every mount is also here.

This result that in my estimation, that a release upgrade of the main nfs-server
from feisty to gutsy will not resolve the problem and I have to stuck on the
old 1.0.9-2ubuntu1 nfs-kernel-server package.

In the current state the nfs-kernel-server package in feisty and guts is not
usable for a nfs-server with more as occasional load.

Best Regards,

H.-Dirk Schmitt


-- System Information:
Debian Release: 4.0
  APT prefers feisty-updates
  APT policy: (500, 'feisty-updates'), (500, 'feisty-security'), (500, 'feisty-proposed'), (500, 'feisty-backports'), (500, 'feisty'), (500, 'edgy-security')
Architecture: amd64 (x86_64)
Shell:  /bin/sh linked to /bin/bash
Kernel: Linux 2.6.20-16-server
Locale: LANG=de_DE.88591, LC_CTYPE=de_DE.88591 (charmap=UTF-8) (ignored: LC_ALL set to de_DE.utf8)

Versions of packages nfs-kernel-server depends on:
ii  l 1.39+1.40-WIP-2006.11.14+dfsg-2ubuntu1 block device id library
ii  l 2.6.1-1ubuntu9                         GNU C Library: Shared libraries
ii  l 1.39+1.40-WIP-2006.11.14+dfsg-2ubuntu1 common error description library
ii  l 0.10-4build1                           A mechanism-switch gssapi library
ii  l 1.4.4-5ubuntu3.3                       MIT Kerberos runtime libraries
ii  l 0.18-0build1                           An nfs idmapping library
ii  l 0.14-2ubuntu1.2                        allows secure rpc communication us
ii  l 7.6.dbs-11ubuntu0.1                    Wietse Venema's TCP wrappers libra
ii  l 3.1-22ubuntu3                          Linux Standard Base 3.1 init scrip
ii  n 1:1.0.12-4                             NFS support files common to client
ii  u 2.0017ubuntu1                          Update Configuration File: preserv

nfs-kernel-server recommends no packages.

-- no debconf information