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Change cpufreq_ondemand to tread SCHED_IDLE time as idle time

Bug 12482 [email protected] 1 participant 2 messages Jan 18, 2011 1 message not in the archive

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https://bugzilla.kernel.org/show_bug.cgi?id=12482

Robert Bradbury <[email protected]> changed:

What |Removed |Added
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CC| |[email protected]

Len Brown <[email protected]> changed:

What |Removed |Added
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             Status|REOPENED                    |RESOLVED
                 CC|                            |[email protected]
         Resolution|                            |DOCUMENTED
         Regression|---                         |No

--- Comment #10 from Robert Bradbury <[email protected]> 2010-06-25 07:15:41 --- Comments on Gentoo Bug #287463 and Kernel Bugs #14066, #14771 and #16072 may be related to this. It is clear from my experience with cpufreq_ondemand and acpi-cpufreq since Linux 2.6.30 is that there are very few people who really understand the issues involved here. The general tone from the "kernel" developers seems to be that cpufreq_ondemand (and indirectly p4-clockmod.c) are "deprecated" in favor of using acpi-cpufreq. This is without taking into account that for acpi-cpufreq to work correctly it needs an Enhanced Intel Speedstep processor *and* a compatible ACPI BIOS with _PCT code(*) -- and there are a *lot* (presumably millions) of machines in the world for which this is not the case.

* This only applies to machines with Intel Pentium class processors presumably.

--- Comment #11 from Len Brown <[email protected]> 2011-01-18 08:20:48 ---
re: comment #10
cpufreq has two parts, the policy governor, and the platform driver. It needs one of each to function.

available governors include ondemand, performance, powersave, userspace available drivers include acpi-cpufreq, p4-clockmod, and some amd-specific ones

ondemand is a fully supported governor
acpi-cpufreq is a fully supported driver

p4-clockmod is generally used by mistake when it is used,
and it generally does more harm than it does good.
The only reason that it hasn't been deleted from the source tree is that some people use it to lower the temperature on celeron processors.

re: comment #9

proposals for enhancing the algorithms used in the ondemand should be done on the list, rather than filed as bugs in bugzilla, particularly proposals that involve scheduling classes etc. that may have a variety of uses and require vetting from a variety of experts (who will not see bugzilla entries).

So I'm going to close this sighting as DOCUMENTED. Please submit your cool ideas to the cpufreq list.

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