[Bug 710319] Re: CPU usage is incorrect on server-status page

[Scott Moser]

I'm fairly sure that the bug that was reported here is due to a kernel bug where utime can decrease.
http://kerneltrap.org/mailarchive/linux-kernel/2009/12/2/4514350

I've verified the test program shown in that thread reproduces on my lucid system:
  $ dpkg -S /boot/vmlinuz-$(uname -r)
  linux-image-2.6.32-24-server: /boot/vmlinuz-2.6.32-24-server
  $ dpkg-query --show linux-image-2.6.32-24-server
  linux-image-2.6.32-24-server    2.6.32-24.43

A single test on my natty system with 2.6.38-1-generic did not
reproduce.

Source code review indicates both natty and lucid kernels have [1]
applied.

One way or another this is almost certainly a kernel bug, as mod_status just reads kernel tms.
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[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=0cf55e1ec08bb5a22e068309e2d8ba1180ab4239 

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

** Changed in: apache2 (Ubuntu)
   Importance: Undecided => Medium

** Changed in: apache2 (Ubuntu)
       Status: New => Triaged

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https://bugs.launchpad.net/bugs/710319

Title:
  CPU usage is incorrect on server-status page