[Bug 58761] related_cpus truncated with acpi-cpufreq driver on kernel 3.9.3

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https://bugzilla.kernel.org/show_bug.cgi?id=58761


Benoit Pradelle <b.pradelle@gmail.com> changed:

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--- Comment #14 from Benoit Pradelle <b.pradelle@gmail.com>  2013-05-30 16:51:31 ---
I totally agree with Jean-Philippe: some information is lost with the 3.9
version and this information *is* useful to correctly set CPU frequencies. So
either the related_cpus field meaning should be restored or a new field should
be added.

If you doubt that such information is valuable, please consider all the runtime
DVFS controllers such as beta adaptive [1], or CPU MISER [2]. Those systems, to
be ported on current multicore processors, have to take a great care of the
actually applied CPU frequency (not only that requested per core but the one
actually in use). If it is impossible to determine what cores share the same
frequency, it is impossible to perform such kind of DVFS on multicore CPUs in a
portable way.

If you think that related_cpus is misleading (and I'd totally agree with you on
that), then maybe a new field is required.


[1] C.-h. Hsu and W.-c. Feng, “A power-aware run-time system for
high-performance computing,” in Proceedings of the 2005 ACM/IEEE conference on
Supercomputing.
[2] R. Ge, X. Feng, W. chun Feng, and K. Cameron, “CPU MISER: A
performance-directed, run-time system for power-aware clusters,” in Parallel
Processing, 2007. ICPP 2007.

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