Commit 17bc14b7 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Revert "sched: Update_cfs_shares at period edge" 



This reverts commit f269ae04.

It turns out it causes a very noticeable interactivity regression with
CONFIG_SCHED_AUTOGROUP (test-case: "make -j32" of the kernel in a
terminal window, while scrolling in a browser - the autogrouping means
that the two end up in separate cgroups, and the browser should be
smooth as silk despite the high load).

Says Paul Turner:
 "It seems that the update-throttling on the wake-side is reducing the
  interactive tasks' ability to preempt.  While I suspect the right
  longer term answer here is force these updates only in the
  cross-cgroup case; this is less trivial.  For this release I believe
  the right answer is either going to be a revert or restore the updates
  on the enqueue-side."

Reported-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Bisected-by: default avatarMike Galbraith <efault@gmx.de>
Acked-by: default avatarPaul Turner <pjt@google.com>
Acked-by: default avatarIngo Molnar <mingo@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7313264b

kernel/sched/fair.c

+8 −10
Original line number Diff line number Diff line
@@ -1265,7 +1265,6 @@ static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq, int force_update) 
	}



	__update_cfs_rq_tg_load_contrib(cfs_rq, force_update);

	update_cfs_shares(cfs_rq);

}



static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
@@ -1475,8 +1474,9 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 
	 * Update run-time statistics of the 'current'.

	 */

	update_curr(cfs_rq);

	account_entity_enqueue(cfs_rq, se);

	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);

	account_entity_enqueue(cfs_rq, se);

	update_cfs_shares(cfs_rq);



	if (flags & ENQUEUE_WAKEUP) {

		place_entity(cfs_rq, se, 0);
@@ -1549,6 +1549,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 
	 * Update run-time statistics of the 'current'.

	 */

	update_curr(cfs_rq);

	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);



	update_stats_dequeue(cfs_rq, se);

	if (flags & DEQUEUE_SLEEP) {
@@ -1568,8 +1569,8 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 


	if (se != cfs_rq->curr)

		__dequeue_entity(cfs_rq, se);

	se->on_rq = 0;

	account_entity_dequeue(cfs_rq, se);

	dequeue_entity_load_avg(cfs_rq, se, flags & DEQUEUE_SLEEP);



	/*

	 * Normalize the entity after updating the min_vruntime because the
@@ -1583,7 +1584,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags) 
	return_cfs_rq_runtime(cfs_rq);



	update_min_vruntime(cfs_rq);

	se->on_rq = 0;

	update_cfs_shares(cfs_rq);

}



/*
@@ -2595,8 +2596,8 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
		if (cfs_rq_throttled(cfs_rq))

			break;



		update_cfs_shares(cfs_rq);

		update_entity_load_avg(se, 1);

		update_cfs_rq_blocked_load(cfs_rq, 0);

	}



	if (!se) {
@@ -2656,8 +2657,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags) 
		if (cfs_rq_throttled(cfs_rq))

			break;



		update_cfs_shares(cfs_rq);

		update_entity_load_avg(se, 1);

		update_cfs_rq_blocked_load(cfs_rq, 0);

	}



	if (!se) {
@@ -5837,11 +5838,8 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares) 
		se = tg->se[i];

		/* Propagate contribution to hierarchy */

		raw_spin_lock_irqsave(&rq->lock, flags);

		for_each_sched_entity(se) {

		for_each_sched_entity(se)

			update_cfs_shares(group_cfs_rq(se));

			/* update contribution to parent */

			update_entity_load_avg(se, 1);

		}

		raw_spin_unlock_irqrestore(&rq->lock, flags);

	}

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