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Commit 523e979d authored by Vincent Guittot's avatar Vincent Guittot Committed by Ingo Molnar
Browse files

sched/core: Use PELT for scale_rt_capacity() 



The utilization of the CPU by RT, DL and IRQs are now tracked with
PELT so we can use these metrics instead of rt_avg to evaluate the remaining
capacity available for CFS class.

scale_rt_capacity() behavior has been changed and now returns the remaining
capacity available for CFS instead of a scaling factor because RT, DL and
IRQ provide now absolute utilization value.

The same formula as schedutil is used:

  IRQ util_avg + (1 - IRQ util_avg / max capacity ) * /Sum rq util_avg

but the implementation is different because it doesn't return the same value
and doesn't benefit of the same optimization.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Morten.Rasmussen@arm.com
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: claudio@evidence.eu.com
Cc: daniel.lezcano@linaro.org
Cc: dietmar.eggemann@arm.com
Cc: joel@joelfernandes.org
Cc: juri.lelli@redhat.com
Cc: luca.abeni@santannapisa.it
Cc: patrick.bellasi@arm.com
Cc: quentin.perret@arm.com
Cc: rjw@rjwysocki.net
Cc: valentin.schneider@arm.com
Cc: viresh.kumar@linaro.org
Link: http://lkml.kernel.org/r/1530200714-4504-10-git-send-email-vincent.guittot@linaro.org


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent dfa444dc

kernel/sched/deadline.c

+0 −2
Original line number Diff line number Diff line
@@ -1180,8 +1180,6 @@ static void update_curr_dl(struct rq *rq) 
	curr->se.exec_start = now;

	cgroup_account_cputime(curr, delta_exec);



	sched_rt_avg_update(rq, delta_exec);



	if (dl_entity_is_special(dl_se))

		return;

kernel/sched/fair.c

+22 −22
Original line number Diff line number Diff line
@@ -7551,39 +7551,39 @@ static inline int get_sd_load_idx(struct sched_domain *sd, 
static unsigned long scale_rt_capacity(int cpu)

{

	struct rq *rq = cpu_rq(cpu);

	u64 total, used, age_stamp, avg;

	s64 delta;



	/*

	 * Since we're reading these variables without serialization make sure

	 * we read them once before doing sanity checks on them.

	 */

	age_stamp = READ_ONCE(rq->age_stamp);

	avg = READ_ONCE(rq->rt_avg);

	delta = __rq_clock_broken(rq) - age_stamp;



	if (unlikely(delta < 0))

		delta = 0;

	unsigned long max = arch_scale_cpu_capacity(NULL, cpu);

	unsigned long used, free;

#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)

	unsigned long irq;

#endif



	total = sched_avg_period() + delta;

#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)

	irq = READ_ONCE(rq->avg_irq.util_avg);



	used = div_u64(avg, total);

	if (unlikely(irq >= max))

		return 1;

#endif



	if (likely(used < SCHED_CAPACITY_SCALE))

		return SCHED_CAPACITY_SCALE - used;

	used = READ_ONCE(rq->avg_rt.util_avg);

	used += READ_ONCE(rq->avg_dl.util_avg);



	if (unlikely(used >= max))

		return 1;



	free = max - used;

#if defined(CONFIG_IRQ_TIME_ACCOUNTING) || defined(CONFIG_PARAVIRT_TIME_ACCOUNTING)

	free *= (max - irq);

	free /= max;

#endif

	return free;

}



static void update_cpu_capacity(struct sched_domain *sd, int cpu)

{

	unsigned long capacity = arch_scale_cpu_capacity(sd, cpu);

	unsigned long capacity = scale_rt_capacity(cpu);

	struct sched_group *sdg = sd->groups;



	cpu_rq(cpu)->cpu_capacity_orig = capacity;



	capacity *= scale_rt_capacity(cpu);

	capacity >>= SCHED_CAPACITY_SHIFT;

	cpu_rq(cpu)->cpu_capacity_orig = arch_scale_cpu_capacity(sd, cpu);



	if (!capacity)

		capacity = 1;

kernel/sched/pelt.c

+1 −1
Original line number Diff line number Diff line
@@ -237,7 +237,7 @@ ___update_load_avg(struct sched_avg *sa, unsigned long load, unsigned long runna 
	 */

	sa->load_avg = div_u64(load * sa->load_sum, divider);

	sa->runnable_load_avg =	div_u64(runnable * sa->runnable_load_sum, divider);

	sa->util_avg = sa->util_sum / divider;

	WRITE_ONCE(sa->util_avg, sa->util_sum / divider);

}



/*

kernel/sched/rt.c

+0 −2
Original line number Diff line number Diff line
@@ -973,8 +973,6 @@ static void update_curr_rt(struct rq *rq) 
	curr->se.exec_start = now;

	cgroup_account_cputime(curr, delta_exec);



	sched_rt_avg_update(rq, delta_exec);



	if (!rt_bandwidth_enabled())

		return;