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[Gordon <kmputerguy@xxxxxxxxx>]

Public bug reported:

I have a clean install of 14.04 on an i7-860 with 16GB RAM.

I'm using NFS to share a home directory.  The volume is ~2TB, formatted
JFS, and it has a single client.

I recently noticed that I had a [kworker] process using 100% CPU:

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                      
 9253 root      20   0       0      0      0 R  99.9  0.0   0:30.17 [kworker/3:1]                

Rebooting didn't help.

After some troubleshooting I found that it went away immediately when I
stopped the nfs-kernel-server daemon.  When I start it, it comes back
after a minute or two, still using 99-100% CPU.  The load goes away when
the client is turned off and the NFS server is restarted, but it comes
back as soon as it reconnects.

The only line in /etc/exports is:
/home 192.168.1.0/24(rw,sync,no_root_squash)

version_signature:
Ubuntu 3.13.0-24.47-generic 3.13.9


# dpkg -l nfs-kernel-server
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name           Version      Architecture Description
+++-==============-============-============-==================================
ii  nfs-kernel-ser 1:1.2.8-6ubu amd64        support for NFS kernel server


Description:    Ubuntu 14.04 LTS
Release:        14.04


I don't think this is related to my hardware but I can provide lspci output if necessary.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1318116

Title:
  kworker uses 100% CPU when nfs-kernel-server is active

Status in “linux” package in Ubuntu:
  New

Bug description:
  I have a clean install of 14.04 on an i7-860 with 16GB RAM.

  I'm using NFS to share a home directory.  The volume is ~2TB,
  formatted JFS, and it has a single client.

  I recently noticed that I had a [kworker] process using 100% CPU:

    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                      
   9253 root      20   0       0      0      0 R  99.9  0.0   0:30.17 [kworker/3:1]                

  Rebooting didn't help.

  After some troubleshooting I found that it went away immediately when
  I stopped the nfs-kernel-server daemon.  When I start it, it comes
  back after a minute or two, still using 99-100% CPU.  The load goes
  away when the client is turned off and the NFS server is restarted,
  but it comes back as soon as it reconnects.

  The only line in /etc/exports is:
  /home 192.168.1.0/24(rw,sync,no_root_squash)

  version_signature:
  Ubuntu 3.13.0-24.47-generic 3.13.9


  # dpkg -l nfs-kernel-server
  Desired=Unknown/Install/Remove/Purge/Hold
  | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
  |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
  ||/ Name           Version      Architecture Description
  +++-==============-============-============-==================================
  ii  nfs-kernel-ser 1:1.2.8-6ubu amd64        support for NFS kernel server

  
  Description:    Ubuntu 14.04 LTS
  Release:        14.04

  
  I don't think this is related to my hardware but I can provide lspci output if necessary.

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