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Diffstat (limited to 'Documentation/cpu-freq/intel-pstate.txt')
| -rw-r--r-- | Documentation/cpu-freq/intel-pstate.txt | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt index 5528d6d59687..198b2ef88aec 100644 --- a/Documentation/cpu-freq/intel-pstate.txt +++ b/Documentation/cpu-freq/intel-pstate.txt @@ -48,7 +48,7 @@ In addition to the frequency-controlling interfaces provided by the cpufreq core, the driver provides its own sysfs files to control the P-State selection. These files have been added to /sys/devices/system/cpu/intel_pstate/. Any changes made to these files are applicable to all CPUs (even in a -multi-package system). +multi-package system, Refer to later section on placing "Per-CPU limits"). max_perf_pct: Limits the maximum P-State that will be requested by the driver. It states it as a percentage of the available performance. The @@ -120,6 +120,25 @@ frequency is fictional for Intel Core processors. Even if the scaling driver selects a single P-State, the actual frequency the processor will run at is selected by the processor itself. +Per-CPU limits + +The kernel command line option "intel_pstate=per_cpu_perf_limits" forces +the intel_pstate driver to use per-CPU performance limits. When it is set, +the sysfs control interface described above is subject to limitations. +- The following controls are not available for both read and write + /sys/devices/system/cpu/intel_pstate/max_perf_pct + /sys/devices/system/cpu/intel_pstate/min_perf_pct +- The following controls can be used to set performance limits, as far as the +architecture of the processor permits: + /sys/devices/system/cpu/cpu*/cpufreq/scaling_max_freq + /sys/devices/system/cpu/cpu*/cpufreq/scaling_min_freq + /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor +- User can still observe turbo percent and number of P-States from + /sys/devices/system/cpu/intel_pstate/turbo_pct + /sys/devices/system/cpu/intel_pstate/num_pstates +- User can read write system wide turbo status + /sys/devices/system/cpu/no_turbo + Tuning Intel P-State driver When the performance can be tuned using PID (Proportional Integral |