backporting timer fix to dapper

Brian Eaton eaton.lists at
Wed Jul 19 02:55:57 UTC 2006

Hi folks -

Is there any chance that some fixes from the 2.6.16 kernel tree could
be backported to Dapper?  There is a bug in the 2.6.15 kernel that
causes timer interrupts to go missing on some laptops, leading to
serious performance problems.  Symptoms include horrible bad graphics,
audio and keyboard performance, and high power consumption.  The only
consistent workaround seems to be to set max_cstate to either 1 or 2,
though some people report that switching from the 686 to the 386
kernel helps.

An explanation of the problem may be found here:

Venkatesh's initial series of three patches was later supplemented
with a couple of others.  I've done a little bit of digging, and I
think a total of six patches are actually needed.  These apply cleanly
to the current dapper kernel, and together they fix the problem:


There are several open dapper bugs that I think all have the same root
cause, the missing timer interrupts.  I didn't do anything like an
exhaustive search through the bug database, but I suspect all of these
are related:

30557 - definitely this problem
34641 - maybe
44391 - maybe
44912 - probably
50153 - probably
50341 - definitely
53404 - definitely

This seems like a fairly large change to make to the dapper kernel,
but the main fix has been in the trees for about six
months, with the last tweak (making the fix apply to AMD CPUs as well
as Intel) in March.  The fix ought to be solid at this point.

Thanks for the work you've put in to Ubuntu.  It's a pleasure to use.


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