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Commit ce6c1311 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: disable forced preemption by default 



Implement feature bit to disable forced preemption. This way
it can be checked whether a workload is overscheduling or not.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e62dd02e

kernel/sched.c

+3 −1
Original line number Diff line number Diff line
@@ -444,13 +444,15 @@ enum { 
	SCHED_FEAT_START_DEBIT		= 2,

	SCHED_FEAT_TREE_AVG             = 4,

	SCHED_FEAT_APPROX_AVG           = 8,

	SCHED_FEAT_WAKEUP_PREEMPT	= 16,

};



const_debug unsigned int sysctl_sched_features =

		SCHED_FEAT_NEW_FAIR_SLEEPERS	*1 |

		SCHED_FEAT_START_DEBIT		*1 |

		SCHED_FEAT_TREE_AVG		*0 |

		SCHED_FEAT_APPROX_AVG		*0;

		SCHED_FEAT_APPROX_AVG		*0 |

		SCHED_FEAT_WAKEUP_PREEMPT	*1;



#define sched_feat(x) (sysctl_sched_features & SCHED_FEAT_##x)

kernel/sched_fair.c

+13 −11
Original line number Diff line number Diff line
@@ -626,7 +626,7 @@ static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr) 
	 */

	update_curr(cfs_rq);



	if (cfs_rq->nr_running > 1)

	if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))

		check_preempt_tick(cfs_rq, curr);

}
@@ -828,6 +828,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) 
		return;

	}



	if (sched_feat(WAKEUP_PREEMPT)) {

		while (!is_same_group(se, pse)) {

			se = parent_entity(se);

			pse = parent_entity(pse);
@@ -841,6 +842,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p) 
		if (delta > gran)

			resched_task(curr);

	}

}



static struct task_struct *pick_next_task_fair(struct rq *rq)

{