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>hifive-unleashed-5.1
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@ -139,6 +139,30 @@ architecture of the processor permits:
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- User can read write system wide turbo status
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- User can read write system wide turbo status
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/sys/devices/system/cpu/no_turbo
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/sys/devices/system/cpu/no_turbo
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Support of energy performance hints
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It is possible to provide hints to the HWP algorithms in the processor
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to be more performance centric to more energy centric. When the driver
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is using HWP, two additional cpufreq sysfs attributes are presented for
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each logical CPU.
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These attributes are:
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- energy_performance_available_preferences
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- energy_performance_preference
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To get list of supported hints:
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$ cat energy_performance_available_preferences
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default performance balance_performance balance_power power
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The current preference can be read or changed via cpufreq sysfs
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attribute "energy_performance_preference". Reading from this attribute
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will display current effective setting. User can write any of the valid
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preference string to this attribute. User can always restore to power-on
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default by writing "default".
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Since threads can migrate to different CPUs, this is possible that the
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new CPU may have different energy performance preference than the previous
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one. To avoid such issues, either threads can be pinned to specific CPUs
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or set the same energy performance preference value to all CPUs.
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Tuning Intel P-State driver
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Tuning Intel P-State driver
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When the performance can be tuned using PID (Proportional Integral
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When the performance can be tuned using PID (Proportional Integral
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