Fork of reMarkable kernel https://github.com/reMarkable/linux
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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. Idle notifiers will be be handled later and are not included for now. 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> |
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README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.