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SubjectRe: linux-2.6.0-test2: Never using pm_idle (CPU wasting power)
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Christian Vogel said:
> on a Thinkpad 600X I noticed the CPU getting very hot. It turned
> out that pm_idle was never called (which invokes the ACPI pm_idle
> call in this case) and default_idle was used instead.

The amd76x_pm patch[1] also hooks pm_idle, and while I'm not 100% sure
about this (haven't instrumented it all the way), it also appears that
pm_idle is not being called (for up to an hour, in some cases). Sometimes
it takes only a few minutes, and other times, it appears to kick in after
heavy CPU usage (kernel compiles, cpuburn, etc.). After pm_idle is called
once, things seem normal-- after the system quiesces, pm_idle is always
called when nothing is ready to run.

Since the amd76x_pm patch appears to work pretty well under 2.4.x, I get
the feeling that the problem lies in the cpu_idle() function. (But I
realize there could be SMP interactions in this case-- in the amd76x_pm
patch, C2 isn't entered unless both CPUs are idle; hence the need for
further instrumentation.)

[1] http://marc.theaimsgroup.com/?l=linux-kernel&m=105665646000758&w=3

--
Charles Lepple <clepple@ghz.cc>
http://www.ghz.cc/charles/
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