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Subject[PATCH 08/16] sched: add period support for -deadline tasks.
Date
From: Harald Gustafsson <harald.gustafsson@ericsson.com>

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>
Signed-off-by: Juri Lelli <juri.lelli@gmail.com>
---
include/linux/sched.h | 1 +
kernel/sched.c | 15 ++++++++++++---
kernel/sched_dl.c | 10 +++++++---
3 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 416ce99..5961592 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1278,6 +1278,7 @@ 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 1a38ad1..9461958 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3024,6 +3024,7 @@ 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);
@@ -5490,6 +5491,10 @@ __setparam_dl(struct task_struct *p, const struct sched_param2 *param2)
init_dl_task_timer(dl_se);
dl_se->dl_runtime = param2->sched_runtime;
dl_se->dl_deadline = param2->sched_deadline;
+ if (param2->sched_period != 0)
+ dl_se->dl_period = param2->sched_period;
+ else
+ dl_se->dl_period = dl_se->dl_deadline;
dl_se->flags = param2->sched_flags;
dl_se->dl_throttled = 0;
dl_se->dl_new = 1;
@@ -5503,19 +5508,23 @@ __getparam_dl(struct task_struct *p, struct sched_param2 *param2)
param2->sched_priority = p->rt_priority;
param2->sched_runtime = dl_se->dl_runtime;
param2->sched_deadline = dl_se->dl_deadline;
+ param2->sched_period = dl_se->dl_period;
param2->sched_flags = dl_se->flags;
}

/*
* 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
+ * greater than deadline.
*/
static bool
__checkparam_dl(const struct sched_param2 *prm)
{
- return prm && (&prm->sched_deadline) != 0 &&
- (s64)(&prm->sched_deadline - &prm->sched_runtime) >= 0;
+ return prm && prm->sched_deadline != 0 &&
+ (prm->sched_period == 0 ||
+ (s64)(prm->sched_period - prm->sched_deadline) >= 0) &&
+ (s64)(prm->sched_deadline - prm->sched_runtime) >= 0;
}

/*
diff --git a/kernel/sched_dl.c b/kernel/sched_dl.c
index 11c9b8d..8682ee2 100644
--- a/kernel/sched_dl.c
+++ b/kernel/sched_dl.c
@@ -266,7 +266,7 @@ 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;
}

@@ -293,7 +293,11 @@ 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)
{
@@ -312,7 +316,7 @@ static bool dl_entity_overflow(struct sched_dl_entity *dl_se, u64 t)
* to the (absolute) deadline. Therefore, overflowing the u64
* type is very unlikely to occur in both cases.
*/
- left = dl_se->dl_deadline * dl_se->runtime;
+ left = dl_se->dl_period * dl_se->runtime;
right = (dl_se->deadline - t) * dl_se->dl_runtime;

return dl_time_before(right, left);
--
1.7.5.4


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