Commit-ID: b95202a3b6bb8715a716dbdb15cdb82bf622260b
Gitweb: http://git.kernel.org/tip/b95202a3b6bb8715a716dbdb15cdb82bf622260b
Author: Tommaso Cucinotta <tommaso.cucinotta@xxxxxxxx>
AuthorDate: Fri, 9 Sep 2016 19:45:17 +0200
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
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.cucinotta@xxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Juri Lelli <juri.lelli@xxxxxxx>
Reviewed-by: Luca Abeni <luca.abeni@xxxxxxxx>
Reviewed-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: linux-dl@xxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1473443117-11794-2-git-send-email-tommaso.cucinotta@xxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
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
=====================
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