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3 Commits

Author SHA1 Message Date
Len Brown
eca0bdd326 Merge branches 'turbostat' and 'x86_energy_perf_policy' into tools 2011-01-11 23:06:28 -05:00
Len Brown
d5532ee7b4 tools: create power/x86/x86_energy_perf_policy
MSR_IA32_ENERGY_PERF_BIAS first became available on Westmere Xeon.
It is implemented in all Sandy Bridge processors -- mobile, desktop and server.
It is expected to become increasingly important in subsequent generations.

x86_energy_perf_policy is a user-space utility to set the
hardware energy vs performance policy hint in the processor.
Most systems would benefit from "x86_energy_perf_policy normal"
at system startup, as the hardware default is maximum performance
at the expense of energy efficiency.

See x86_energy_perf_policy.8 man page for more information.

Background:

Linux-2.6.36 added "epb" to /proc/cpuinfo to indicate
if an x86 processor supports MSR_IA32_ENERGY_PERF_BIAS,
without actually modifying the MSR.

In March, 2010, Venkatesh Pallipadi proposed a small driver
that programmed MSR_IA32_ENERGY_PERF_BIAS, based on
the cpufreq governor in use.  It also offered
a boot-time cmdline option to override.
http://lkml.org/lkml/2010/3/4/457
But hiding the hardware policy behind the
governor choice was deemed "kinda icky".

In June, 2010, I proposed a generic user/kernel API to
generalize the power/performance policy trade-off.
"RFC: /sys/power/policy_preference"
http://lkml.org/lkml/2010/6/16/399
That is my preference for implementing this capability,
but I received no support on the list.

So in September, 2010, I sent x86_energy_perf_policy.c to LKML,
a user-space utility that scribbles directly to the MSR.
http://lkml.org/lkml/2010/9/28/246

Here is that same utility, after responding to some review feedback,
to live in tools/power/, where it is easily found.

Signed-off-by: Len Brown <len.brown@intel.com>
2011-01-11 23:02:21 -05:00
Len Brown
103a8fea9b tools: create power/x86/turbostat
turbostat is a Linux tool to observe proper operation
of Intel(R) Turbo Boost Technology.

turbostat displays the actual processor frequency
on x86 processors that include APERF and MPERF MSRs.

Note that turbostat is of limited utility on Linux
kernels 2.6.29 and older, as acpi_cpufreq cleared
APERF/MPERF up through that release.

On Intel Core i3/i5/i7 (Nehalem) and newer processors,
turbostat also displays residency in idle power saving states,
which are necessary for diagnosing any cpuidle issues
that may have an effect on turbo-mode.

See the turbostat.8 man page for example usage.

Signed-off-by: Len Brown <len.brown@intel.com>
2011-01-11 22:46:02 -05:00