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Schedtune is the framework we use in Android to allow userspace task classification and provides a CGroup controller which has two attributes per group. * schedtune.boost * schedtune.prefer_idle Schedtune itself provides task and CPU utilization boosting. EAS in the fair scheduler uses boosted utilization and prefer_idle status to control the algorithm used for wakeup task placement. Boosting: The task utilization signal, which is derived from PELT signals and properly scaled to be architecture and frequency invariant, is used by EAS as an estimation of the task requirements in terms of CPU bandwidth. Schedtune allows userspace to assign a percentage boost to each group and this boost is used to calculate an additional utilization margin. The margin added to the original utilization is: 1. computed based on the "boosting strategy" in use 2. proportional to boost value defined by the "taskgroup" value The boosted signal is used by EAS for task placement, and boosted CPU utilization (if boosted tasks are running) is given when schedutil requests utilization. Prefer_idle: When this attribute is 1 for a group, this is used as a signal from userspace that tasks in this group need to be serviced with the minimum latency possible. Previous versions of schedtune had much more functionality around allowing a more tuneable tradeoff between performand and energy, however this has not been used a lot up until now. If necessary, we can easily resurrect it based upon old code. Signed-off-by: Patrick Bellasi <patrick.bellasi@arm.com> Signed-off-by: Chris Redpath <chris.redpath@arm.com> (cherry-picked from commit 159c14f0397790405b9e8435184366b31f2ed15b) [ - Removed tracepoints (to be added in a separate patch) - Integrated boosted_cpu_util() with cpu_util_cfs() - Backported Patrick's util_est related fixes from android-4.14 ] Signed-off-by: Quentin Perret <quentin.perret@arm.com> Change-Id: Ie2fd63d82f604f34bcbc7e1ca9b5af1bdcc037e0 |
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
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.