MAN page from CentOS 7 kernel-plus-tools-3.10.0-1160.21.1.el7.centos.plus.x86_64.rpm
Section: Maintenance Commands (8)Index
x86_energy_perf_policy - read or write MSR_IA32_ENERGY_PERF_BIAS
allows 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.
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.
runs only as root.
Written by Len Brown <len.brownAATTintel.com>
- SEE ALSO
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