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https://lkml.org/lkml/2016/9/14/208 Interactive governor has lived in Android sources for a very long time and this commit is based on the code present in following branch: https://android.googlesource.com/kernel/common android-4.4 The Interactive governor is designed for latency-sensitive workloads, such as interactive user interfaces like the mobile phones and tablets. The interactive governor aims to be significantly more responsive to ramp CPU quickly up when CPU-intensive activity begins. Existing governors sample CPU load at a particular rate, typically every X ms and then update the frequency from a work-handler. This can lead to under-powering UI threads for the period of time during which the user begins interacting with a previously-idle system until the next sample period happens. The 'interactive' governor uses a different approach. A real-time thread is used for scaling up, giving the remaining tasks the CPU performance benefit, unlike existing governors which are more likely to schedule ramp-up work to occur after your performance starved tasks have completed. The Android version of interactive governor also checks whether to scale the CPU frequency up soon after coming out of idle. When the CPU comes out of idle, the governor check if the CPU sampling is overdue or not. If yes, it immediately starts the sampling. Otherwise, the utilization hooks from the scheduler handle the sampling later. If the CPU is very busy from exiting idle to when the evaluation happens, then it assumes that the CPU is under-powered and ramps it to MAX speed. If the CPU was not sufficiently busy to immediately ramp to MAX speed, then the 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 core of this code is written and maintained (in Android repositories) by Mike Chan and Todd Poyner over a long period of time. Vireshk has made changes to to the governor to align it with the current practices followed with mainline governors, like using utilization hooks from the scheduler and handling kobject (for governor's sysfs directory) in a race free manner. And of course this included general cleanup of the governor as well. Signed-off-by: Mike Chan <mike@android.com> Signed-off-by: Todd Poynor <toddpoynor@google.com> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org> Change-Id: Ib5e8d1dab0fa3cc5ba79b7a554c8dde35435cbdb [AmitP: Cherry-picked this version from https://git.kernel.org/cgit/linux/kernel/git/vireshk/pm.git/log/?h=cpufreq/interactive-idle-notifier. Also refactored and folded https://lkml.org/lkml/2016/9/14/209 patch into this unified patch.] Signed-off-by: Amit Pundir <amit.pundir@linaro.org> Signed-off-by: Liang Chen <cl@rock-chips.com> (cherry picked from https://android.googlesource.com/kernel/msm commit 33f7a05d4e82c81841af20e6a944a4c3f9b2973e) |
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