[RFC][PATCH 09/22] sched: add period support for -deadline tasks

[Raistlin <raistlin@linux.it>]

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Make it possible to specify a period (different or equal than
deadline) for -deadline tasks.

Signed-off-by: Harald Gustafsson <harald.gustafsson@ericsson.com>
Signed-off-by: Dario Faggioli <raistlin@linux.it>
---
 include/linux/sched.h |    1 +
 kernel/sched.c        |   12 +++++++++++-
 kernel/sched_dl.c     |    8 ++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index f25d3a6..83fa2b5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1251,6 +1251,7 @@ struct sched_dl_entity {
 	 */
 	u64 dl_runtime;		/* maximum runtime for each instance 	*/
 	u64 dl_deadline;	/* relative deadline of each instance	*/
+	u64 dl_period;		/* separation of two instances (period) */
 
 	/*
 	 * Actual scheduling parameters. Initialized with the values above,
diff --git a/kernel/sched.c b/kernel/sched.c
index 7f0780c..4491f7d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2708,6 +2708,7 @@ static void __sched_fork(struct task_struct *p)
 	hrtimer_init(&p->dl.dl_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
 	p->dl.dl_runtime = p->dl.runtime = 0;
 	p->dl.dl_deadline = p->dl.deadline = 0;
+	p->dl.dl_period = 0;
 	p->dl.flags = 0;
 
 	INIT_LIST_HEAD(&p->rt.run_list);
@@ -4789,6 +4790,10 @@ __setparam_dl(struct task_struct *p, const struct sched_param_ex *param_ex)
 	init_dl_task_timer(dl_se);
 	dl_se->dl_runtime = timespec_to_ns(&param_ex->sched_runtime);
 	dl_se->dl_deadline = timespec_to_ns(&param_ex->sched_deadline);
+	if (timespec_to_ns(&param_ex->sched_period) != 0)
+		dl_se->dl_period = timespec_to_ns(&param_ex->sched_period);
+	else
+		dl_se->dl_period = dl_se->dl_deadline;
 	dl_se->flags = param_ex->sched_flags;
 	dl_se->dl_throttled = 0;
 	dl_se->dl_new = 1;
@@ -4802,6 +4807,7 @@ __getparam_dl(struct task_struct *p, struct sched_param_ex *param_ex)
 	param_ex->sched_priority = p->rt_priority;
 	param_ex->sched_runtime = ns_to_timespec(dl_se->dl_runtime);
 	param_ex->sched_deadline = ns_to_timespec(dl_se->dl_deadline);
+	param_ex->sched_period = ns_to_timespec(dl_se->dl_period);
 	param_ex->sched_flags = dl_se->flags;
 	param_ex->curr_runtime = ns_to_timespec(dl_se->runtime);
 	param_ex->curr_deadline = ns_to_timespec(dl_se->deadline);
@@ -4810,7 +4816,8 @@ __getparam_dl(struct task_struct *p, struct sched_param_ex *param_ex)
 /*
  * This function validates the new parameters of a -deadline task.
  * We ask for the deadline not being zero, and greater or equal
- * than the runtime.
+ * than the runtime, as well as the period of being zero or
+ * not greater than deadline.
  */
 static bool
 __checkparam_dl(const struct sched_param_ex *prm, bool kthread)
@@ -4822,6 +4829,9 @@ __checkparam_dl(const struct sched_param_ex *prm, bool kthread)
 		return kthread;
 
 	return timespec_to_ns(&prm->sched_deadline) != 0 &&
+	       (timespec_to_ns(&prm->sched_period) == 0 ||
+		timespec_compare(&prm->sched_period,
+				 &prm->sched_deadline) >= 0) &&
 	       timespec_compare(&prm->sched_deadline,
 				&prm->sched_runtime) >= 0;
 }
diff --git a/kernel/sched_dl.c b/kernel/sched_dl.c
index 1bb4308..31fb771 100644
--- a/kernel/sched_dl.c
+++ b/kernel/sched_dl.c
@@ -263,7 +263,7 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
 	 * arbitrary large.
 	 */
 	while (dl_se->runtime <= 0) {
-		dl_se->deadline += dl_se->dl_deadline;
+		dl_se->deadline += dl_se->dl_period;
 		dl_se->runtime += dl_se->dl_runtime;
 	}
 
@@ -290,7 +290,11 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se)
  * assigned (function returns true if it can).
  *
  * For this to hold, we must check if:
- *   runtime / (deadline - t) < dl_runtime / dl_deadline .
+ *   runtime / (deadline - t) < dl_runtime / dl_period .
+ *
+ * Notice that the bandwidth check is done against the period. For
+ * task with deadline equal to period this is the same of using
+ * dl_deadline instead of dl_period in the equation above.
  */
 static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
 {
-- 
1.7.2.3


-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
----------------------------------------------------------------------
Dario Faggioli, ReTiS Lab, Scuola Superiore Sant'Anna, Pisa  (Italy)

http://blog.linux.it/raistlin / raistlin@ekiga.net /
dario.faggioli@jabber.org

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