kernel_optimize_test

History

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
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x86_energy_perf_policy	tools: create power/x86/x86_energy_perf_policy	2011-01-11 23:02:21 -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

x86_energy_perf_policy

tools: create power/x86/x86_energy_perf_policy

2011-01-11 23:02:21 -05:00