[RFC v2 1/7] Track the active utilisation

Luca Abeni
2016-04-01T15:21:28Z

The active utilisation here is defined as the total utilisation of the
active (TASK_RUNNING) tasks queued on a runqueue. Hence, it is increased
when a task wakes up and is decreased when a task blocks.
This might need to be fixed / improved by decreasing the active
utilisation at the so-called "0-lag time" instead of when the task blocks.

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
---
kernel/sched/deadline.c | 32 +++++++++++++++++++++++++++++++-
kernel/sched/sched.h | 6 ++++++
2 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c7a036f..3c64ebf 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -43,6 +43,22 @@ static inline int on_dl_rq(struct sched_dl_entity *dl_se)
return !RB_EMPTY_NODE(&dl_se->rb_node);
}

+static void add_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+ u64 se_bw = dl_se->dl_bw;
+
+ dl_rq->running_bw += se_bw;
+}
+
+static void sub_running_bw(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
+{
+ u64 se_bw = dl_se->dl_bw;
+
+ dl_rq->running_bw -= se_bw;
+ if (WARN_ON(dl_rq->running_bw < 0))
+ dl_rq->running_bw = 0;
+}
+
static inline int is_leftmost(struct task_struct *p, struct dl_rq *dl_rq)
{
struct sched_dl_entity *dl_se = &p->dl;
@@ -510,6 +526,8 @@ static void update_dl_entity(struct sched_dl_entity *dl_se,
struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
struct rq *rq = rq_of_dl_rq(dl_rq);

+ add_running_bw(dl_se, dl_rq);
+
if (dl_time_before(dl_se->deadline, rq_clock(rq)) ||
dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) {
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
@@ -957,8 +975,10 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
*/
- if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))
+ if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH)) {
+ add_running_bw(&p->dl, &rq->dl);
return;
+ }

enqueue_dl_entity(&p->dl, pi_se, flags);

@@ -976,6 +996,8 @@ static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
{
update_curr_dl(rq);
__dequeue_task_dl(rq, p, flags);
+ if (flags & DEQUEUE_SLEEP)
+ sub_running_bw(&p->dl, &rq->dl);
}

/*
@@ -1210,6 +1232,8 @@ static void task_fork_dl(struct task_struct *p)
static void task_dead_dl(struct task_struct *p)
{
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
+ struct dl_rq *dl_rq = dl_rq_of_se(&p->dl);
+ struct rq *rq = rq_of_dl_rq(dl_rq);

/*
* Since we are TASK_DEAD we won't slip out of the domain!
@@ -1218,6 +1242,9 @@ static void task_dead_dl(struct task_struct *p)
/* XXX we should retain the bw until 0-lag */
dl_b->total_bw -= p->dl.dl_bw;
raw_spin_unlock_irq(&dl_b->lock);
+
+ if (task_on_rq_queued(p))
+ sub_running_bw(&p->dl, &rq->dl);
}

static void set_curr_task_dl(struct rq *rq)
@@ -1697,6 +1724,9 @@ static void switched_from_dl(struct rq *rq, struct task_struct *p)
if (!start_dl_timer(p))
__dl_clear_params(p);

+ if (task_on_rq_queued(p))
+ sub_running_bw(&p->dl, &rq->dl);
+
/*
* Since this might be the only -deadline task on the rq,
* this is the right place to try to pull some other one
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index e6d4a3f..bc05c29 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -520,6 +520,12 @@ struct dl_rq {
#else
struct dl_bw dl_bw;
#endif
+ /*
+ * "Active utilization" for this runqueue: increased when a
+ * task wakes up (becomes TASK_RUNNING) and decreased when a
+ * task blocks
+ */
+ s64 running_bw;
};

#ifdef CONFIG_SMP
--
2.5.0