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>
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>
---
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
=====================
--
2.7.4
