[Bug 879334] Re: nfsd from nfs-kernel-server very slow and system load from 25%-100% from nfsd

[Thomas Anantharaman]

I have been struggling at work with the same problem for the last few months, and accidentally stumbled on a fix that seems to work under Ubuntu 12.04 (3.5.0-32-generic 64-bit kernel) :
 
1. On clients set rsize=8192,wsize=8192 in /etc/fstab (Smaller values of rsize,wsize will also work, but reduce throughput).

Previously with rsize=wsize=32K, any 2 clients writing large files to
our server (with 1 Gbit NICs for clients and 2x1Gbit NICs for the
server) would freeze : all clients would appear to hang on accessing the
NFS server, but the hang would eventually resolve itself (after several
hours of writes at around 100k/sec on the server grinding away
continuously with jbd2, or within minutes if one of the 2 clients with
the large writes temporarily had its ethernet turned off and then back
on after the other client's write had completed).

Now 4 clients can write to the server at 53 MB/sec saturating the server
bandwidth at 210 MB/sec and the network and server remain responsive
from other interactive clients.

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Title:
  nfsd from nfs-kernel-server very slow and system load from 25%-100%
  from nfsd

Status in “linux” package in Ubuntu:
  Incomplete
Status in “nfs-utils” package in Ubuntu:
  Confirmed
Status in “linux” package in Debian:
  Incomplete

Bug description:
  I have a diskless ubuntu 10.10 machine which I boot regularly using
  pxe-boot from another ubuntu machine where I have the root filesystem
  of the diskless machine exported over nfs.

  I set it up about a year ago using 10.10. In the mean while the server
  machine got upgraded to 11.04 and as of yesterday to 11.10.

  After the upgrade to 11.10 the diskless machine is dead slow (most of
  the times it wont even boot completely) and the load on the server
  machine is high (25%-100% as shown from top). If in the middle of the
  diskless computer booting I do a restart of the nfs server, the client
  computer proceeds with the boot a bit more and then it gets stuck
  again. I have to restart and nfs-server 3-4 times in order to get the
  gdm login screen at the client machine

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: nfs-kernel-server 1:1.2.4-1ubuntu2
  ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
  Uname: Linux 3.0.0-12-generic i686
  ApportVersion: 1.23-0ubuntu3
  Architecture: i386
  Date: Fri Oct 21 12:53:02 2011
  ProcEnviron:
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: nfs-utils
  UpgradeStatus: Upgraded to oneiric on 2011-10-20 (1 days ago)

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