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authorDan Willemsen <dwillemsen@nvidia.com>2011-11-30 21:51:56 -0800
committerDan Willemsen <dwillemsen@nvidia.com>2011-11-30 21:51:56 -0800
commit68529c0f36074be88ee937634fb9433e69c96388 (patch)
tree00c842c0eff6a2b946e1c11a1bdf2d632535e0a7 /Documentation/cpu-freq/governors.txt
parentf9a10833c7a12ce1244685eba88848bb88bbd43f (diff)
parent3ac6e2e8106ac304c56b9435c907b2b3bda27a09 (diff)
Merge branch 'korg-android-tegra-3.1' into after-upstream-android
Conflicts: arch/arm/mach-tegra/Kconfig arch/arm/mach-tegra/board-ventana.c drivers/misc/Kconfig drivers/video/tegra/dc/hdmi.c Signed-off-by: Dan Willemsen <dwillemsen@nvidia.com>
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diff --git a/Documentation/cpu-freq/governors.txt b/Documentation/cpu-freq/governors.txt
index e74d0a2eb1cf..51b1cd360c33 100644
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+++ 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
@@ -193,6 +194,43 @@ governor but for the opposite direction. For example when set to its
default value of '20' it means that if the CPU usage needs to be below
20% between samples to have the frequency decreased.
+
+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. 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.
+
+The tuneable values for this governor are:
+
+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.
+
+go_maxspeed_load: The CPU load at which to ramp to max speed. Default
+is 85.
+
+timer_rate: Sample rate for reevaluating cpu load when the system is
+not idle. Default is 30000 uS.
+
3. The Governor Interface in the CPUfreq Core
=============================================