Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
tools/power x86_energy_perf_policy.8: Emphasize preference for SW interfaces
This tool was originally written when Linux had no standard
interface for EPB, or HWP support.
Retain the capability to manage a system w/o any kernel PM support,
but prefer the standard kernel interfaces, when avaialble.
(not doing so led to a confusing conflict between a p-state limit
request made via cpufreq and modified by the intel-pstate driver,
versus the raw MSR write made by this utility)
Signed-off-by: Len Brown <len.brown@intel.com>
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tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8
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tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8
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.\" Distributed under the GPL, Copyleft 1994.
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.TH X86_ENERGY_PERF_POLICY 8
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.SH NAME
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x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Specific Registers
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x86_energy_perf_policy \- Manage Energy vs. Performance Policy
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.SH SYNOPSIS
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.B x86_energy_perf_policy
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.RB "[ options ] [ scope ] [field \ value]"
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.SH DESCRIPTION
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\fBx86_energy_perf_policy\fP
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displays and updates energy-performance policy settings specific to
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Intel Architecture Processors. Settings are accessed via Model Specific Register (MSR)
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updates, no matter if the Linux cpufreq sub-system is enabled or not.
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Intel Architecture Processors. It summarizes settings available
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in standard Linux interfaces (eg. cpufreq),
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and also decodes underlying Model Specific Register (MSRs).
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While \fBx86_energy_perf_policy\fP can manage energy-performance policy
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using only MSR access, it prefers standard
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Linux kernel interfaces, when they are available.
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.SH BACKGROUND
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Policy in MSR_IA32_ENERGY_PERF_BIAS (EPB)
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may affect a wide range of hardware decisions,
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such as how aggressively the hardware enters and exits CPU idle states (C-states)
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.SH FILES
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.ta
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.nf
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/dev/cpu/*/msr
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EPB: /sys/devices/system/cpu/cpu*/power/energy_perf_bias
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EPP: /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference
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MSR: /dev/cpu/*/msr
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.fi
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.SH "SEE ALSO"
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.nf