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

[Jeff Ebert]

There is an upstream bug here:
https://bugzilla.kernel.org/show_bug.cgi?id=40912

I have tried the latest mainstream kernel (3.5.0) using the instructions here:
https://wiki.ubuntu.com/KernelTeam/GitKernelBuild

I still see the high CPU load on the NFS server.

I then reversed the patch suggested in the above bug.

$ git show 9660439861aa8dbd5e2b8087f33e20760c2c9afc
commit 9660439861aa8dbd5e2b8087f33e20760c2c9afc
Author: Olga Kornievskaia <aglo at citi.umich.edu>
Date:   Tue Oct 21 14:13:47 2008 -0400

    svcrpc: take advantage of tcp autotuning
    
I also reversed the patch mentioned here manually, since I could not find the commit hash for it
http://lists.openwall.net/netdev/2012/01/20/81

Unfortunately, this patched version of 3.5.0 does not boot. I may have
screwed up something else along the way, but I wanted to report this in
case somebody has more time to experiment.

This particular patch looks like an ongoing problem for nfsd. It was
reverted due to performance issues in 2009.

commit 7f4218354fe312b327af06c3d8c95ed5f214c8ca
Author: J. Bruce Fields <bfields at citi.umich.edu>
Date:   Wed May 27 18:51:06 2009 -0400

    nfsd: Revert "svcrpc: take advantage of tcp autotuning"
    
    This reverts commit 47a14ef1af48c696b214ac168f056ddc79793d0e "svcrpc:
    take advantage of tcp autotuning", which uncovered some further problems
    in the server rpc code, causing significant performance regressions in
    common cases.
    
    We will likely reinstate this patch after releasing 2.6.30 and applying
    some work on the underlying fixes to the problem (developed by Trond).
    
    Reported-by: Jeff Moyer <jmoyer at redhat.com>
    Cc: Olga Kornievskaia <aglo at citi.umich.edu>
    Cc: Jim Rees <rees at umich.edu>
    Cc: Trond Myklebust <trond.myklebust at fys.uio.no>
    Signed-off-by: J. Bruce Fields <bfields at citi.umich.edu>

It was reintroduced in May 2011,  commit
a74d70b63f1a0230831bcca3145d85ae016f9d4c .

Hope this helps somebody...


** Bug watch added: Linux Kernel Bug Tracker #40912
   http://bugzilla.kernel.org/show_bug.cgi?id=40912

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https://bugs.launchpad.net/bugs/879334

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

Status in “nfs-utils” package in Ubuntu:
  Confirmed

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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