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Commit 07881166 authored by Juri Lelli's avatar Juri Lelli Committed by Ingo Molnar
Browse files

sched/deadline: Make bandwidth enforcement scale-invariant 



Apply frequency and CPU scale-invariance correction factor to bandwidth
enforcement (similar to what we already do to fair utilization tracking).

Each delta_exec gets scaled considering current frequency and maximum
CPU capacity; which means that the reservation runtime parameter (that
need to be specified profiling the task execution at max frequency on
biggest capacity core) gets thus scaled accordingly.

Signed-off-by: default avatarJuri Lelli <juri.lelli@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Claudio Scordino <claudio@evidence.eu.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Luca Abeni <luca.abeni@santannapisa.it>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: alessio.balsini@arm.com
Cc: bristot@redhat.com
Cc: dietmar.eggemann@arm.com
Cc: joelaf@google.com
Cc: juri.lelli@redhat.com
Cc: mathieu.poirier@linaro.org
Cc: morten.rasmussen@arm.com
Cc: patrick.bellasi@arm.com
Cc: rjw@rjwysocki.net
Cc: rostedt@goodmis.org
Cc: tkjos@android.com
Cc: tommaso.cucinotta@santannapisa.it
Cc: vincent.guittot@linaro.org
Link: http://lkml.kernel.org/r/20171204102325.5110-9-juri.lelli@redhat.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 7e1a9208

kernel/sched/deadline.c

+22 −4
Original line number Diff line number Diff line
@@ -1151,7 +1151,8 @@ static void update_curr_dl(struct rq *rq) 
{

	struct task_struct *curr = rq->curr;

	struct sched_dl_entity *dl_se = &curr->dl;

	u64 delta_exec;

	u64 delta_exec, scaled_delta_exec;

	int cpu = cpu_of(rq);



	if (!dl_task(curr) || !on_dl_rq(dl_se))

		return;
@@ -1185,9 +1186,26 @@ static void update_curr_dl(struct rq *rq) 
	if (dl_entity_is_special(dl_se))

		return;



	if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM))

		delta_exec = grub_reclaim(delta_exec, rq, &curr->dl);

	dl_se->runtime -= delta_exec;

	/*

	 * For tasks that participate in GRUB, we implement GRUB-PA: the

	 * spare reclaimed bandwidth is used to clock down frequency.

	 *

	 * For the others, we still need to scale reservation parameters

	 * according to current frequency and CPU maximum capacity.

	 */

	if (unlikely(dl_se->flags & SCHED_FLAG_RECLAIM)) {

		scaled_delta_exec = grub_reclaim(delta_exec,

						 rq,

						 &curr->dl);

	} else {

		unsigned long scale_freq = arch_scale_freq_capacity(cpu);

		unsigned long scale_cpu = arch_scale_cpu_capacity(NULL, cpu);



		scaled_delta_exec = cap_scale(delta_exec, scale_freq);

		scaled_delta_exec = cap_scale(scaled_delta_exec, scale_cpu);

	}



	dl_se->runtime -= scaled_delta_exec;



throttle:

	if (dl_runtime_exceeded(dl_se) || dl_se->dl_yielded) {

kernel/sched/fair.c

+0 −2
Original line number Diff line number Diff line
@@ -3089,8 +3089,6 @@ static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) 
	return c1 + c2 + c3;

}



#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)



/*

 * Accumulate the three separate parts of the sum; d1 the remainder

 * of the last (incomplete) period, d2 the span of full periods and d3

kernel/sched/sched.h

+2 −0
Original line number Diff line number Diff line
@@ -156,6 +156,8 @@ static inline int task_has_dl_policy(struct task_struct *p) 
	return dl_policy(p->policy);

}



#define cap_scale(v, s) ((v)*(s) >> SCHED_CAPACITY_SHIFT)



/*

 * !! For sched_setattr_nocheck() (kernel) only !!

 *