Commit a4f9a0e5 authored by Vincent Guittot's avatar Vincent Guittot Committed by Peter Zijlstra
Browse files

sched/fair: Remove redundant call to cpufreq_update_util() 



With commit

  bef69dd8 ("sched/cpufreq: Move the cfs_rq_util_change() call to cpufreq_update_util()")

update_load_avg() has become the central point for calling cpufreq
(not including the update of blocked load). This change helps to
simplify further the number of calls to cpufreq_update_util() and to
remove last redundant ones. With update_load_avg(), we are now sure
that cpufreq_update_util() will be called after every task attachment
to a cfs_rq and especially after propagating this event down to the
util_avg of the root cfs_rq, which is the level that is used by
cpufreq governors like schedutil to set the frequency of a CPU.

The SCHED_CPUFREQ_MIGRATION flag forces an early call to cpufreq when
the migration happens in a cgroup whereas util_avg of root cfs_rq is
not yet updated and this call is duplicated with the one that happens
immediately after when the migration event reaches the root cfs_rq.
The dedicated flag SCHED_CPUFREQ_MIGRATION is now useless and can be
removed. The interface of attach_entity_load_avg() can also be
simplified accordingly.

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lkml.kernel.org/r/1579083620-24943-1-git-send-email-vincent.guittot@linaro.org
parent 3d817689

include/linux/sched/cpufreq.h

+0 −1
Original line number Diff line number Diff line
@@ -9,7 +9,6 @@ 
 */



#define SCHED_CPUFREQ_IOWAIT	(1U << 0)

#define SCHED_CPUFREQ_MIGRATION	(1U << 1)



#ifdef CONFIG_CPU_FREQ

struct cpufreq_policy;

kernel/sched/fair.c

+7 −7
Original line number Diff line number Diff line
@@ -801,7 +801,7 @@ void post_init_entity_util_avg(struct task_struct *p) 
		 * For !fair tasks do:

		 *

		update_cfs_rq_load_avg(now, cfs_rq);

		attach_entity_load_avg(cfs_rq, se, 0);

		attach_entity_load_avg(cfs_rq, se);

		switched_from_fair(rq, p);

		 *

		 * such that the next switched_to_fair() has the
@@ -3114,7 +3114,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq, int flags) 
{

	struct rq *rq = rq_of(cfs_rq);



	if (&rq->cfs == cfs_rq || (flags & SCHED_CPUFREQ_MIGRATION)) {

	if (&rq->cfs == cfs_rq) {

		/*

		 * There are a few boundary cases this might miss but it should

		 * get called often enough that that should (hopefully) not be
@@ -3521,7 +3521,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq) 
 * Must call update_cfs_rq_load_avg() before this, since we rely on

 * cfs_rq->avg.last_update_time being current.

 */

static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)

static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	u32 divider = LOAD_AVG_MAX - 1024 + cfs_rq->avg.period_contrib;
@@ -3557,7 +3557,7 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s 


	add_tg_cfs_propagate(cfs_rq, se->avg.load_sum);



	cfs_rq_util_change(cfs_rq, flags);

	cfs_rq_util_change(cfs_rq, 0);



	trace_pelt_cfs_tp(cfs_rq);

}
@@ -3615,7 +3615,7 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s 
		 *

		 * IOW we're enqueueing a task on a new CPU.

		 */

		attach_entity_load_avg(cfs_rq, se, SCHED_CPUFREQ_MIGRATION);

		attach_entity_load_avg(cfs_rq, se);

		update_tg_load_avg(cfs_rq, 0);



	} else if (decayed) {
@@ -3872,7 +3872,7 @@ static inline void update_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s 
static inline void remove_entity_load_avg(struct sched_entity *se) {}



static inline void

attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) {}

attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}

static inline void

detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) {}
@@ -10436,7 +10436,7 @@ static void attach_entity_cfs_rq(struct sched_entity *se) 


	/* Synchronize entity with its cfs_rq */

	update_load_avg(cfs_rq, se, sched_feat(ATTACH_AGE_LOAD) ? 0 : SKIP_AGE_LOAD);

	attach_entity_load_avg(cfs_rq, se, 0);

	attach_entity_load_avg(cfs_rq, se);

	update_tg_load_avg(cfs_rq, false);

	propagate_entity_cfs_rq(se);

}

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