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SubjectRe: [PATCH v2] sched/rt: fix call to cpufreq_update_util
Le Thursday 17 May 2018 à 11:32:06 (+0200), Peter Zijlstra a écrit :
> On Thu, May 17, 2018 at 11:05:30AM +0200, Peter Zijlstra wrote:
> > Hurm.. I think this is also wrong. See how dequeue_rt_stack() is also
> > called from the enqueue path. Also, nothing calls cpufreq_update_util()
> > on the throttle path now.

Yes I missed the point that rt_entities were dequeued then re-enqueued when
a task was either enqueued or dequeued.

That's also means that enqueue_top_rt_rq() is always called when a task is
enqueued or dequeued and also when groups are throttled or unthrottled
In fact, the only point where it's not called, is when root rt_rq is
throttled. So I have prepared the patch below which call cpufreq_update util
in enqueue_top_rt_rq() and also when we throttle the root rt_rq.
According to the tests I have done , it seems to work for enqueue/dequeue and
throttle/unthrottle use cases.

I have re-used your rt_rq_is_runnable() which takes into account rt_queued

---
kernel/sched/cpufreq_schedutil.c | 2 +-
kernel/sched/rt.c | 16 ++++++++++------
kernel/sched/sched.h | 5 +++++
3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index e13df95..1751f96 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -185,7 +185,7 @@ static unsigned long sugov_aggregate_util(struct sugov_cpu *sg_cpu)
struct rq *rq = cpu_rq(sg_cpu->cpu);
unsigned long util;

- if (rq->rt.rt_nr_running) {
+ if (rt_rq_is_runnable(&rq->rt)) {
util = sg_cpu->max;
} else {
util = sg_cpu->util_dl;
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 7aef6b4..d6b9517 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -508,8 +508,11 @@ static void sched_rt_rq_dequeue(struct rt_rq *rt_rq)

rt_se = rt_rq->tg->rt_se[cpu];

- if (!rt_se)
+ if (!rt_se) {
dequeue_top_rt_rq(rt_rq);
+ /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
+ cpufreq_update_util(rq_of_rt_rq(rt_rq), 0);
+ }
else if (on_rt_rq(rt_se))
dequeue_rt_entity(rt_se, 0);
}
@@ -1001,8 +1004,6 @@ dequeue_top_rt_rq(struct rt_rq *rt_rq)
sub_nr_running(rq, rt_rq->rt_nr_running);
rt_rq->rt_queued = 0;

- /* Kick cpufreq (see the comment in kernel/sched/sched.h). */
- cpufreq_update_util(rq, 0);
}

static void
@@ -1014,11 +1015,14 @@ enqueue_top_rt_rq(struct rt_rq *rt_rq)

if (rt_rq->rt_queued)
return;
- if (rt_rq_throttled(rt_rq) || !rt_rq->rt_nr_running)
+
+ if (rt_rq_throttled(rt_rq))
return;

- add_nr_running(rq, rt_rq->rt_nr_running);
- rt_rq->rt_queued = 1;
+ if (rt_rq->rt_nr_running) {
+ add_nr_running(rq, rt_rq->rt_nr_running);
+ rt_rq->rt_queued = 1;
+ }

/* Kick cpufreq (see the comment in kernel/sched/sched.h). */
cpufreq_update_util(rq, 0);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c9895d3..bbebcfe 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -609,6 +609,11 @@ struct rt_rq {
#endif
};

+static inline bool rt_rq_is_runnable(struct rt_rq *rt_rq)
+{
+ return rt_rq->rt_queued && rt_rq->rt_nr_running;
+}
+
/* Deadline class' related fields in a runqueue */
struct dl_rq {
/* runqueue is an rbtree, ordered by deadline */
--
2.7.4




> >
> > And talking about throttle; I think we wanted to check rt_queued in that
> > case.
>
> Bah, clearly you also want to update on unthrottle.. but I think there's
> more buggered wrt throtteling.




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