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| author | Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> | 2016-12-07 00:32:17 +0300 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2016-12-08 03:43:05 +0300 |
| commit | bf006e149a5717a4614d44a62090ae98775af7a0 (patch) | |
| tree | f3dd9733c2be117d9faef9be96444ba0c74989fd | |
| parent | 984edbdccc6ff01b953492f72296685ce3ea2497 (diff) | |
| download | linux-bf006e149a5717a4614d44a62090ae98775af7a0.tar.xz | |
Documentation: intel_pstate: Document HWP energy/performance hints
Updated documentation for the support of energy performance hint in
the HWP mode.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Subject & changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | Documentation/cpu-freq/intel-pstate.txt | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/Documentation/cpu-freq/intel-pstate.txt b/Documentation/cpu-freq/intel-pstate.txt index 198b2ef88aec..1953994ef5e6 100644 --- a/Documentation/cpu-freq/intel-pstate.txt +++ b/Documentation/cpu-freq/intel-pstate.txt @@ -139,6 +139,30 @@ architecture of the processor permits: - User can read write system wide turbo status /sys/devices/system/cpu/no_turbo +Support of energy performance hints +It is possible to provide hints to the HWP algorithms in the processor +to be more performance centric to more energy centric. When the driver +is using HWP, two additional cpufreq sysfs attributes are presented for +each logical CPU. +These attributes are: + - energy_performance_available_preferences + - energy_performance_preference + +To get list of supported hints: +$ cat energy_performance_available_preferences + default performance balance_performance balance_power power + +The current preference can be read or changed via cpufreq sysfs +attribute "energy_performance_preference". Reading from this attribute +will display current effective setting. User can write any of the valid +preference string to this attribute. User can always restore to power-on +default by writing "default". + +Since threads can migrate to different CPUs, this is possible that the +new CPU may have different energy performance preference than the previous +one. To avoid such issues, either threads can be pinned to specific CPUs +or set the same energy performance preference value to all CPUs. + Tuning Intel P-State driver When the performance can be tuned using PID (Proportional Integral |