Commits
Michael Turquette committed 5c905a08612
sched: scheduler-driven cpu frequency selection Scheduler-driven CPU frequency selection hopes to exploit both per-task and global information in the scheduler to improve frequency selection policy, achieving lower power consumption, improved responsiveness/performance, and less reliance on heuristics and tunables. For further discussion on the motivation of this integration see [0]. This patch implements a shim layer between the Linux scheduler and the cpufreq subsystem. The interface accepts capacity requests from the CFS, RT and deadline sched classes. The requests from each sched class are summed on each CPU with a margin applied to the CFS and RT capacity requests to provide some headroom. Deadline requests are expected to be precise enough given their nature to not require headroom. The maximum total capacity request for a CPU in a frequency domain drives the requested frequency for that domain. Policy is determined by both the sched classes and this shim layer. Note that this algorithm is event-driven. There is no polling loop to check cpu idle time nor any other method which is unsynchronized with the scheduler, aside from a throttling mechanism to ensure frequency changes are not attempted faster than the hardware can accommodate them. Thanks to Juri Lelli <juri.lelli@arm.com> for contributing design ideas, code and test results, and to Ricky Liang <jcliang@chromium.org> for initialization and static key inc/dec fixes. [0] http://article.gmane.org/gmane.linux.kernel/1499836 [smuckle@linaro.org: various additions and fixes, revised commit text] CC: Ricky Liang <jcliang@chromium.org> Signed-off-by: Michael Turquette <mturquette@baylibre.com> Signed-off-by: Juri Lelli <juri.lelli@arm.com> Signed-off-by: Steve Muckle <smuckle@linaro.org>