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MAN page from CentOS 7 kernel-plus-tools-3.10.0-1160.21.1.el7.centos.plus.x86_64.rpm

X86_ENERGY_PERF_POLICY

Section: Maintenance Commands (8)
Index 

NAME

x86_energy_perf_policy - read or write MSR_IA32_ENERGY_PERF_BIAS 

SYNOPSIS

x86_energy_perf_policy[-c cpu][-v]-r
x86_energy_perf_policy[-c cpu][-v]'performance'
x86_energy_perf_policy[-c cpu][-v]'normal'
x86_energy_perf_policy[-c cpu][-v]'powersave'
x86_energy_perf_policy[-c cpu][-v]n
 

DESCRIPTION

x86_energy_perf_policyallows software to conveyits policy for the relative importance of performanceversus energy savings to the processor.

The processor uses this information in model-specific wayswhen it must select trade-offs between performance andenergy efficiency.

This policy hint does not supersede Processor Performance states(P-states) or CPU Idle power states (C-states), but allowssoftware to have influence where it would otherwise be unableto express a preference.

For example, this setting may tell the hardware howaggressively or conservatively to control frequencyin the "turbo range" above the explicitly OS-controlledP-state frequency range. It may also tell the hardwarehow aggressively is should enter the OS requested C-states.

Support for this feature is indicated by CPUID.06H.ECX.bit3per the Intel Architectures Software Developer's Manual.

 

Options

-c limits operation to a single CPU.The default is to operate on all CPUs.Note that MSR_IA32_ENERGY_PERF_BIAS is defined perlogical processor, but that the initial implementationsof the MSR were shared among all processors in each package.

-v increases verbosity. By defaultx86_energy_perf_policy is silent.

-r is for "read-only" mode - the unchanged stateis read and displayed.

performanceSet a policy where performance is paramount.The processor will be unwilling to sacrifice any performancefor the sake of energy saving. This is the hardware default.

normalSet a policy with a normal balance between performance and energy efficiency.The processor will tolerate minor performance compromisefor potentially significant energy savings.This reasonable default for most desktops and servers.

powersaveSet a policy where the processor can accepta measurable performance hit to maximize energy efficiency.

nSet MSR_IA32_ENERGY_PERF_BIAS to the specified number.The range of valid numbers is 0-15, where 0 is maximumperformance and 15 is maximum energy efficiency.

 

NOTES

x86_energy_perf_policy runs only as root. 

FILES

/dev/cpu/*/msr

 

SEE ALSO

msr(4)

 

AUTHORS

Written by Len Brown <len.brownAATTintel.com>

 

Index

NAME
SYNOPSIS
DESCRIPTION
Options
NOTES
FILES
SEE ALSO
AUTHORS

This document was created byman2html,using the manual pages.