Commit e0c2ff90 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched/fair: Remove sched_feat(START_DEBIT) 



With the introduction of avg_vruntime() there is no need to use worse
approximations. Take the 0-lag point as starting point for inserting
new tasks.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20230531124603.722361178@infradead.org
parent af4cf404

kernel/sched/fair.c

+1 −20
Original line number Diff line number Diff line
@@ -906,16 +906,6 @@ static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se) 
	return slice;

}



/*

 * We calculate the vruntime slice of a to-be-inserted task.

 *

 * vs = s/w

 */

static u64 sched_vslice(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	return calc_delta_fair(sched_slice(cfs_rq, se), se);

}



#include "pelt.h"

#ifdef CONFIG_SMP
@@ -4862,16 +4852,7 @@ static inline bool entity_is_long_sleeper(struct sched_entity *se) 
static void

place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)

{

	u64 vruntime = cfs_rq->min_vruntime;



	/*

	 * The 'current' period is already promised to the current tasks,

	 * however the extra weight of the new task will slow them down a

	 * little, place the new task so that it fits in the slot that

	 * stays open at the end.

	 */

	if (initial && sched_feat(START_DEBIT))

		vruntime += sched_vslice(cfs_rq, se);

	u64 vruntime = avg_vruntime(cfs_rq);



	/* sleeps up to a single latency don't count. */

	if (!initial) {

kernel/sched/features.h

+0 −6
Original line number Diff line number Diff line
@@ -6,12 +6,6 @@ 
 */

SCHED_FEAT(GENTLE_FAIR_SLEEPERS, true)



/*

 * Place new tasks ahead so that they do not starve already running

 * tasks

 */

SCHED_FEAT(START_DEBIT, true)



/*

 * Prefer to schedule the task we woke last (assuming it failed

 * wakeup-preemption), since its likely going to consume data we