kernel-packages team mailing list archive

["Christopher M. Penalver" <christopher.m.penalver@xxxxxxxxx>]

Shaun Thomas, could you please gather the apport-collect following
https://help.ubuntu.com/community/ReportingBugs#Filing_bugs_when_off-
line ?

** Tags added: needs-kernel-logs regression-updated

** Tags removed: regression-updated
** Tags added: regression-update

** Tags added: needs-bisect

** Tags removed: needs-bisect
** Tags added: needs-reverse-bisect

** Changed in: linux (Ubuntu)
       Status: Confirmed => Incomplete

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https://bugs.launchpad.net/bugs/1084264

Title:
  Kernel 3.2.0-33 Introduces Ridiculous / Impossible Load Averages

Status in “linux” package in Ubuntu:
  Incomplete

Bug description:
  After upgrading to the 3.2.0-33 kernel, our load averages have been
  very, very odd. Here is a sample sar -q line:

  15:05:02      runq-sz  plist-sz   ldavg-1   ldavg-5  ldavg-15   blocked
  15:05:21            2       322     44.02     12.51     14.08         1

  A run queue size of 2, with a load average of 44? So I wrote a script
  to track run queue and uninterruptable sleep, since both contribute to
  load average. Script is attached. Sample output during a run:

  Stat Time		Run+Sleep	Load Avg
  2012-11-28 15:47:53	2		71.54
  2012-11-28 15:47:54	1		71.54
  2012-11-28 15:47:55	1		71.54
  2012-11-28 15:47:56	1		71.54
  2012-11-28 15:47:57	1		71.54
  2012-11-28 15:47:58	1		65.81

  This behavior is not observed with kernel 3.2.0-31.

  Problem can be reproduced with a basic pgbench test to simulate busy
  state, but only seems to occur during rapid process cycling. An easy
  simulation:

  for x in {1..100}; do
    pgbench -T 5 -j 2 -c 2 pgbench
    sleep 1
  done

  Test may need to run for several minutes to trigger load spike. It
  will look similar to this:

  Stat Time		Run+Sleep	Load Avg
  2012-11-28 16:01:17	3		10.37
  2012-11-28 16:01:18	3		9.54
  2012-11-28 16:01:19	3		9.54
  2012-11-28 16:01:20	2		9.54
  2012-11-28 16:01:21	5		9.54
  2012-11-28 16:01:22	3		9.54
  2012-11-28 16:01:23	1		47.94

  System info:

  Description:	Ubuntu 12.04.1 LTS
  Release:	12.04
  Linux 3.2.0-33-generic #52-Ubuntu SMP Thu Oct 18 16:29:15 UTC 2012 x86_64
  linux-image-3.2.0-33-generic:
    Installed: 3.2.0-33.52

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