[lug] sluggish machine

Lee Woodworth blug-mail at duboulder.com
Fri May 22 00:53:11 MDT 2009

Davide Del Vento wrote:
> Thanks everybody for the help.
> I'm replying to everything in just a consolidated email.

[... snip lots of interesting stuff ...]

Just a thought. It may be useful to determine how much time the CPU
hog processes spend in the kernel (htop will show % kernel time for
all processes).

If its lots of time in the kernel, like I have had with firefox,
then I tend to suspect X and the kernel more than user space. X has
had for more than a year an occasional issue where it goes into CPU eating
mode (see the gentoo forums, was also showing up on other distros). This
was prevalent about 10-12 months ago, in those cases X would directly
show as being 100% CPU. Was commonly triggered by firefox. Various
video cards, distros and kernels. I never heard of a solid diagnosis of
the problem, it has just slowly improved, but still exists. About 3 months
ago the yahoo home page reliably triggered a 100% CPU binge with firefox 3.0.5
on a 2.6.27 kernel, 1.3.x Xorg. Almost all of the time in kernel mode.
Haven't  tried it after kernel/x-org upgrades to know if its better.

A reason you may be seeing several processes being marked as heavy CPU
users is that a kernel thread has gone haywire. The process accounting
tools I know of don't separate out the time for kernel threads. A long-
lived rogue kernel thread would affect the process accounting for user
processes that context switched in while the rogue was running.

Your kernel is a few versions old. Didn't see info about the X version
in your original post. I would consider upgrading at least X. There have
been changes in the kernel which affect X so it is probably a good idea
to upgrade the kernel if you can.

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