Commit fe8d238e authored by Aaron Lu's avatar Aaron Lu Committed by Peter Zijlstra
Browse files

sched/fair: Propagate load for throttled cfs_rq 



Before task based throttle model, propagating load will stop at a
throttled cfs_rq and that propagate will happen on unthrottle time by
update_load_avg().

Now that there is no update_load_avg() on unthrottle for throttled
cfs_rq and all load tracking is done by task related operations, let the
propagate happen immediately.

While at it, add a comment to explain why cfs_rqs that are not affected
by throttle have to be added to leaf cfs_rq list in
propagate_entity_cfs_rq() per my understanding of commit 0258bdfa
("sched/fair: Fix unfairness caused by missing load decay").

Signed-off-by: default avatarAaron Lu <ziqianlu@bytedance.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarChengming Zhou <chengming.zhou@linux.dev>
parent 5b726e9b

kernel/sched/fair.c

+18 −8
Original line number Diff line number Diff line
@@ -5729,6 +5729,11 @@ static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 
	return cfs_bandwidth_used() && cfs_rq->throttled;

}



static inline bool cfs_rq_pelt_clock_throttled(struct cfs_rq *cfs_rq)

{

	return cfs_bandwidth_used() && cfs_rq->pelt_clock_throttled;

}



/* check whether cfs_rq, or any parent, is throttled */

static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)

{
@@ -6721,6 +6726,11 @@ static inline int cfs_rq_throttled(struct cfs_rq *cfs_rq) 
	return 0;

}



static inline bool cfs_rq_pelt_clock_throttled(struct cfs_rq *cfs_rq)

{

	return false;

}



static inline int throttled_hierarchy(struct cfs_rq *cfs_rq)

{

	return 0;
@@ -13151,10 +13161,13 @@ static void propagate_entity_cfs_rq(struct sched_entity *se) 
{

	struct cfs_rq *cfs_rq = cfs_rq_of(se);



	if (cfs_rq_throttled(cfs_rq))

		return;



	if (!throttled_hierarchy(cfs_rq))

	/*

	 * If a task gets attached to this cfs_rq and before being queued,

	 * it gets migrated to another CPU due to reasons like affinity

	 * change, make sure this cfs_rq stays on leaf cfs_rq list to have

	 * that removed load decayed or it can cause faireness problem.

	 */

	if (!cfs_rq_pelt_clock_throttled(cfs_rq))

		list_add_leaf_cfs_rq(cfs_rq);



	/* Start to propagate at parent */
@@ -13165,10 +13178,7 @@ static void propagate_entity_cfs_rq(struct sched_entity *se) 


		update_load_avg(cfs_rq, se, UPDATE_TG);



		if (cfs_rq_throttled(cfs_rq))

			break;



		if (!throttled_hierarchy(cfs_rq))

		if (!cfs_rq_pelt_clock_throttled(cfs_rq))

			list_add_leaf_cfs_rq(cfs_rq);

	}

}