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- Intel P-state driver
- --------------------
- This driver implements a scaling driver with an internal governor for
- Intel Core processors. The driver follows the same model as the
- Transmeta scaling driver (longrun.c) and implements the setpolicy()
- instead of target(). Scaling drivers that implement setpolicy() are
- assumed to implement internal governors by the cpufreq core. All the
- logic for selecting the current P state is contained within the
- driver; no external governor is used by the cpufreq core.
- Intel SandyBridge+ processors are supported.
- New sysfs files for controlling P state selection have been added to
- /sys/devices/system/cpu/intel_pstate/
- max_perf_pct: limits the maximum P state that will be requested by
- the driver stated as a percentage of the available performance. The
- available (P states) performance may be reduced by the no_turbo
- setting described below.
- min_perf_pct: limits the minimum P state that will be requested by
- the driver stated as a percentage of the max (non-turbo)
- performance level.
- no_turbo: limits the driver to selecting P states below the turbo
- frequency range.
- For contemporary Intel processors, the frequency is controlled by the
- processor itself and the P-states exposed to software are related to
- performance levels. The idea that frequency can be set to a single
- frequency is fiction 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.
- New debugfs files have also been added to /sys/kernel/debug/pstate_snb/
- deadband
- d_gain_pct
- i_gain_pct
- p_gain_pct
- sample_rate_ms
- setpoint
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