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Diffstat (limited to 'Documentation/cpu-freq')
| -rw-r--r-- | Documentation/cpu-freq/governors.txt | 64 |
1 files changed, 32 insertions, 32 deletions
diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt index d44901eedcf8..3732ec162873 100644 --- a/Documentation/cpu-freq/governors.txt +++ b/Documentation/cpu-freq/governors.txt @@ -224,23 +224,8 @@ sampling rate. 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. However, -the governor is more aggressive about scaling the CPU speed up in -response to CPU-intensive activity. - -Sampling the CPU load every X ms can lead to under-powering the CPU -for X ms, leading to dropped frames, stuttering UI, etc. Instead of -sampling the cpu at a specified rate, the interactive governor will -check whether to scale the cpu frequency up soon after coming out of -idle. When the cpu comes out of idle, a timer is configured to fire -within 1-2 ticks. If the cpu is very busy between exiting idle and -when the timer fires then we assume the cpu is underpowered and ramp -to MAX speed. - -If the cpu was not sufficiently busy to immediately ramp to MAX speed, -then governor evaluates the cpu load since the last speed adjustment, -choosing the highest value between that longer-term load or the -short-term load since idle exit to determine the cpu speed to ramp to. +usage, similar to "ondemand" and "conservative" governors, but with a +different set of configurable behaviors. The tuneable values for this governor are: @@ -262,36 +247,51 @@ 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. This is to ensure that the governor has -seen enough historic cpu load data to determine the appropriate -workload. Default is 80000 uS. +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 maximum speed. +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 the intermediate "hi -speed". Default is 85%. +go_hispeed_load: The CPU load at which to ramp to hispeed_freq. +Default is 99%. -above_hispeed_delay: Once speed is set to hispeed_freq, wait for this -long before bumping speed higher in response to continued high load. +above_hispeed_delay: When speed is at or above hispeed_freq, wait for +this long before raising speed in response to continued high load. Default is 20000 uS. -timer_rate: Sample rate for reevaluating cpu load when the system is -not idle. Default is 20000 uS. - -input_boost: If non-zero, boost speed of all CPUs to hispeed_freq on -touchscreen activity. Default is 0. +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: Immediately boost speed of all CPUs to hispeed_freq for -min_sample_time, after which speeds are allowed to drop below +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 ============================================= |