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Diffstat (limited to 'kernel/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8')
-rw-r--r-- | kernel/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 | 104 |
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diff --git a/kernel/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 b/kernel/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 new file mode 100644 index 000000000..8eaaad648 --- /dev/null +++ b/kernel/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 @@ -0,0 +1,104 @@ +.\" This page Copyright (C) 2010 Len Brown <len.brown@intel.com> +.\" Distributed under the GPL, Copyleft 1994. +.TH X86_ENERGY_PERF_POLICY 8 +.SH NAME +x86_energy_perf_policy \- read or write MSR_IA32_ENERGY_PERF_BIAS +.SH SYNOPSIS +.ft B +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB "\-r" +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'performance' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'normal' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB 'powersave' +.br +.B x86_energy_perf_policy +.RB [ "\-c cpu" ] +.RB [ "\-v" ] +.RB n +.br +.SH DESCRIPTION +\fBx86_energy_perf_policy\fP +allows software to convey +its policy for the relative importance of performance +versus energy savings to the processor. + +The processor uses this information in model-specific ways +when it must select trade-offs between performance and +energy efficiency. + +This policy hint does not supersede Processor Performance states +(P-states) or CPU Idle power states (C-states), but allows +software to have influence where it would otherwise be unable +to express a preference. + +For example, this setting may tell the hardware how +aggressively or conservatively to control frequency +in the "turbo range" above the explicitly OS-controlled +P-state frequency range. It may also tell the hardware +how aggressively is should enter the OS requested C-states. + +Support for this feature is indicated by CPUID.06H.ECX.bit3 +per the Intel Architectures Software Developer's Manual. + +.SS Options +\fB-c\fP limits operation to a single CPU. +The default is to operate on all CPUs. +Note that MSR_IA32_ENERGY_PERF_BIAS is defined per +logical processor, but that the initial implementations +of the MSR were shared among all processors in each package. +.PP +\fB-v\fP increases verbosity. By default +x86_energy_perf_policy is silent. +.PP +\fB-r\fP is for "read-only" mode - the unchanged state +is read and displayed. +.PP +.I performance +Set a policy where performance is paramount. +The processor will be unwilling to sacrifice any performance +for the sake of energy saving. This is the hardware default. +.PP +.I normal +Set a policy with a normal balance between performance and energy efficiency. +The processor will tolerate minor performance compromise +for potentially significant energy savings. +This reasonable default for most desktops and servers. +.PP +.I powersave +Set a policy where the processor can accept +a measurable performance hit to maximize energy efficiency. +.PP +.I n +Set MSR_IA32_ENERGY_PERF_BIAS to the specified number. +The range of valid numbers is 0-15, where 0 is maximum +performance and 15 is maximum energy efficiency. + +.SH NOTES +.B "x86_energy_perf_policy " +runs only as root. +.SH FILES +.ta +.nf +/dev/cpu/*/msr +.fi + +.SH "SEE ALSO" +msr(4) +.PP +.SH AUTHORS +.nf +Written by Len Brown <len.brown@intel.com> |