diff options
| author | Len Brown <len.brown@intel.com> | 2025-09-24 11:50:29 -0400 |
|---|---|---|
| committer | Len Brown <len.brown@intel.com> | 2025-09-25 23:12:01 -0400 |
| commit | 66f430522452fe1a8a0fd2198cf9f335125acbfc (patch) | |
| tree | 6d11e55e571c31cc61ea7d22a175245d5ece5700 /tools | |
| parent | a648e0892ccd8c2168c2deae7e12e18a8d596730 (diff) | |
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>
Diffstat (limited to 'tools')
| -rw-r--r-- | tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 index 78c6361898b1..0aa981c18e56 100644 --- a/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 +++ b/tools/power/x86/x86_energy_perf_policy/x86_energy_perf_policy.8 @@ -2,7 +2,7 @@ .\" Distributed under the GPL, Copyleft 1994. .TH X86_ENERGY_PERF_POLICY 8 .SH NAME -x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Specific Registers +x86_energy_perf_policy \- Manage Energy vs. Performance Policy .SH SYNOPSIS .B x86_energy_perf_policy .RB "[ options ] [ scope ] [field \ value]" @@ -19,9 +19,14 @@ x86_energy_perf_policy \- Manage Energy vs. Performance Policy via x86 Model Spe .SH DESCRIPTION \fBx86_energy_perf_policy\fP displays and updates energy-performance policy settings specific to -Intel Architecture Processors. Settings are accessed via Model Specific Register (MSR) -updates, no matter if the Linux cpufreq sub-system is enabled or not. +Intel Architecture Processors. It summarizes settings available +in standard Linux interfaces (eg. cpufreq), +and also decodes underlying Model Specific Register (MSRs). +While \fBx86_energy_perf_policy\fP can manage energy-performance policy +using only MSR access, it prefers standard +Linux kernel interfaces, when they are available. +.SH BACKGROUND Policy in MSR_IA32_ENERGY_PERF_BIAS (EPB) may affect a wide range of hardware decisions, such as how aggressively the hardware enters and exits CPU idle states (C-states) @@ -200,7 +205,9 @@ runs only as root. .SH FILES .ta .nf -/dev/cpu/*/msr +EPB: /sys/devices/system/cpu/cpu*/power/energy_perf_bias +EPP: /sys/devices/system/cpu/cpu*/cpufreq/energy_performance_preference +MSR: /dev/cpu/*/msr .fi .SH "SEE ALSO" .nf |