Commit-ID: b95202a3b6bb8715a716dbdb15cdb82bf622260b Gitweb: http://git.kernel.org/tip/b95202a3b6bb8715a716dbdb15cdb82bf622260b Author: Tommaso Cucinotta <tommaso.cucino...@sssup.it> AuthorDate: Fri, 9 Sep 2016 19:45:17 +0200 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Sat, 10 Sep 2016 11:17:41 +0200
sched/deadline: Document behavior of sched_yield() This is a documentation only patch, explaining the behavior of sched_yield() when a SCHED_DEADLINE task calls it (give up remaining runtime and be throttled until next period begins). Signed-off-by: Tommaso Cucinotta <tommaso.cucino...@sssup.it> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Reviewed-by: Juri Lelli <juri.le...@arm.com> Reviewed-by: Luca Abeni <luca.ab...@unitn.it> Reviewed-by: Daniel Bristot de Oliveira <bris...@redhat.com> Cc: Juri Lelli <juri.le...@gmail.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: linux...@retis.sssup.it Link: http://lkml.kernel.org/r/1473443117-11794-2-git-send-email-tommaso.cucino...@sssup.it Signed-off-by: Ingo Molnar <mi...@kernel.org> --- Documentation/scheduler/sched-deadline.txt | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt index 53a2fe1..8e37b0b 100644 --- a/Documentation/scheduler/sched-deadline.txt +++ b/Documentation/scheduler/sched-deadline.txt @@ -16,6 +16,7 @@ CONTENTS 4.1 System-wide settings 4.2 Task interface 4.3 Default behavior + 4.4 Behavior of sched_yield() 5. Tasks CPU affinity 5.1 SCHED_DEADLINE and cpusets HOWTO 6. Future plans @@ -426,6 +427,23 @@ CONTENTS Finally, notice that in order not to jeopardize the admission control a -deadline task cannot fork. + +4.4 Behavior of sched_yield() +----------------------------- + + When a SCHED_DEADLINE task calls sched_yield(), it gives up its + remaining runtime and is immediately throttled, until the next + period, when its runtime will be replenished (a special flag + dl_yielded is set and used to handle correctly throttling and runtime + replenishment after a call to sched_yield()). + + This behavior of sched_yield() allows the task to wake-up exactly at + the beginning of the next period. Also, this may be useful in the + future with bandwidth reclaiming mechanisms, where sched_yield() will + make the leftoever runtime available for reclamation by other + SCHED_DEADLINE tasks. + + 5. Tasks CPU affinity =====================
