Commit 3a0baa8e authored by Vincent Guittot's avatar Vincent Guittot Committed by Peter Zijlstra
Browse files

sched/fair: Fix entity's lag with run to parity 



When an entity is enqueued without preempting current, we must ensure
that the slice protection is updated to take into account the slice
duration of the newly enqueued task so that its lag will not exceed
its slice (+ tick).

Signed-off-by: default avatarVincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250708165630.1948751-6-vincent.guittot@linaro.org
parent 052c3d87

kernel/sched/fair.c

+13 −3
Original line number Diff line number Diff line
@@ -889,13 +889,13 @@ struct sched_entity *__pick_first_entity(struct cfs_rq *cfs_rq) 
 * When run to parity is disabled, we give a minimum quantum to the running

 * entity to ensure progress.

 */

static inline void set_protect_slice(struct sched_entity *se)

static inline void set_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	u64 slice = normalized_sysctl_sched_base_slice;

	u64 vprot = se->deadline;



	if (sched_feat(RUN_TO_PARITY))

		slice = cfs_rq_min_slice(cfs_rq_of(se));

		slice = cfs_rq_min_slice(cfs_rq);



	slice = min(slice, se->slice);

	if (slice != se->slice)
@@ -904,6 +904,13 @@ static inline void set_protect_slice(struct sched_entity *se) 
	se->vprot = vprot;

}



static inline void update_protect_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)

{

	u64 slice = cfs_rq_min_slice(cfs_rq);



	se->vprot = min_vruntime(se->vprot, se->vruntime + calc_delta_fair(slice, se));

}



static inline bool protect_slice(struct sched_entity *se)

{

	return ((s64)(se->vprot - se->vruntime) > 0);
@@ -5467,7 +5474,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se) 
		__dequeue_entity(cfs_rq, se);

		update_load_avg(cfs_rq, se, UPDATE_TG);



		set_protect_slice(se);

		set_protect_slice(cfs_rq, se);

	}



	update_stats_curr_start(cfs_rq, se);
@@ -8720,6 +8727,9 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int 
	if (__pick_eevdf(cfs_rq, !do_preempt_short) == pse)

		goto preempt;



	if (sched_feat(RUN_TO_PARITY) && do_preempt_short)

		update_protect_slice(cfs_rq, se);



	return;



preempt: