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diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index 219970ba54b7..875eecbed8c8 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -28,6 +28,7 @@ Contents: 2.3 Userspace 2.4 Ondemand 2.5 Conservative +2.6 Interactive 3. The Governor Interface in the CPUfreq Core @@ -218,6 +219,90 @@ a decision on when to decrease the frequency while running in any speed. Load for frequency increase is still evaluated every sampling rate. +2.6 Interactive +--------------- + +The CPUfreq governor "interactive" is designed for latency-sensitive, +interactive workloads. This governor sets the CPU speed depending on +usage, similar to "ondemand" and "conservative" governors, but with a +different set of configurable behaviors. + +The tuneable values for this governor are: + +target_loads: CPU load values used to adjust speed to influence the +current CPU load toward that value. In general, the lower the target +load, the more often the governor will raise CPU speeds to bring load +below the target. The format is a single target load, optionally +followed by pairs of CPU speeds and CPU loads to target at or above +those speeds. Colons can be used between the speeds and associated +target loads for readability. For example: + + 85 1000000:90 1700000:99 + +targets CPU load 85% below speed 1GHz, 90% at or above 1GHz, until +1.7GHz and above, at which load 99% is targeted. If speeds are +specified these must appear in ascending order. Higher target load +values are typically specified for higher speeds, that is, target load +values also usually appear in an ascending order. The default is +target load 90% for all speeds. + +min_sample_time: The minimum amount of time to spend at the current +frequency before ramping down. Default is 80000 uS. + +hispeed_freq: An intermediate "hi speed" at which to initially ramp +when CPU load hits the value specified in go_hispeed_load. If load +stays high for the amount of time specified in above_hispeed_delay, +then speed may be bumped higher. Default is the maximum speed +allowed by the policy at governor initialization time. + +go_hispeed_load: The CPU load at which to ramp to hispeed_freq. +Default is 99%. + +above_hispeed_delay: When speed is at or above hispeed_freq, wait for +this long before raising speed in response to continued high load. +The format is a single delay value, optionally followed by pairs of +CPU speeds and the delay to use at or above those speeds. Colons can +be used between the speeds and associated delays for readability. For +example: + + 80000 1300000:200000 1500000:40000 + +uses delay 80000 uS until CPU speed 1.3 GHz, at which speed delay +200000 uS is used until speed 1.5 GHz, at which speed (and above) +delay 40000 uS is used. If speeds are specified these must appear in +ascending order. Default is 20000 uS. + +timer_rate: Sample rate for reevaluating CPU load when the CPU is not +idle. A deferrable timer is used, such that the CPU will not be woken +from idle to service this timer until something else needs to run. +(The maximum time to allow deferring this timer when not running at +minimum speed is configurable via timer_slack.) Default is 20000 uS. + +timer_slack: Maximum additional time to defer handling the governor +sampling timer beyond timer_rate when running at speeds above the +minimum. For platforms that consume additional power at idle when +CPUs are running at speeds greater than minimum, this places an upper +bound on how long the timer will be deferred prior to re-evaluating +load and dropping speed. For example, if timer_rate is 20000uS and +timer_slack is 10000uS then timers will be deferred for up to 30msec +when not at lowest speed. A value of -1 means defer timers +indefinitely at all speeds. Default is 80000 uS. + +boost: If non-zero, immediately boost speed of all CPUs to at least +hispeed_freq until zero is written to this attribute. If zero, allow +CPU speeds to drop below hispeed_freq according to load as usual. +Default is zero. + +boostpulse: On each write, immediately boost speed of all CPUs to +hispeed_freq for at least the period of time specified by +boostpulse_duration, after which speeds are allowed to drop below +hispeed_freq according to load as usual. + +boostpulse_duration: Length of time to hold CPU speed at hispeed_freq +on a write to boostpulse, before allowing speed to drop according to +load as usual. Default is 80000 uS. + + 3. The Governor Interface in the CPUfreq Core ============================================= |