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| author | Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> | 2016-10-25 13:20:42 -0700 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-11-01 06:04:06 +0100 |
| commit | 9e472f95e480d6746ed8646634e6b11994207015 (patch) | |
| tree | fbaa91caf6fef524d3f6a181581870bd6b20acd1 /Documentation/cpu-freq | |
| parent | 5879f877398a2a5e5006c6e16a4288e9d4c308a1 (diff) | |
| download | lwn-9e472f95e480d6746ed8646634e6b11994207015.tar.gz lwn-9e472f95e480d6746ed8646634e6b11994207015.zip | |
Documentation: intel_pstate: Update per core limits
Document restriction on per core P-State control.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/cpu-freq')
| -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 |