sched: virtual time buddy preemption (3f3a4904) · Commits · 戴 / test

Since we moved wakeup preemption back to virtual time, it makes sense to move the buddy stuff back as well. The purpose of the buddy scheduling is to allow a quickly scheduling pair of tasks to run away from the group as far as a regular busy task would be allowed under wakeup preemption. This has the advantage that the pair can ping-pong for a while, enjoying cache-hotness. Without buddy scheduling other tasks would interleave destroying the cache. Also, it saves a word in cfs_rq. Signed-off-by:

Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by:

Mike Galbraith <efault@gmx.de> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+0 −1

Original line number	Diff line number	Diff line
		@@ -386,7 +386,6 @@ struct cfs_rq {

		u64 exec_clock;
		u64 min_vruntime;
		u64 pair_start;

		struct rb_root tasks_timeline;
		struct rb_node *rb_leftmost;

kernel/sched_fair.c

+4 −6

Original line number	Diff line number	Diff line
		@@ -791,16 +791,14 @@ set_next_entity(struct cfs_rq cfs_rq, struct sched_entity se)
		se->prev_sum_exec_runtime = se->sum_exec_runtime;
		}

		static int
		wakeup_preempt_entity(struct sched_entity curr, struct sched_entity se);

		static struct sched_entity *
		pick_next(struct cfs_rq cfs_rq, struct sched_entity se)
		{
		struct rq *rq = rq_of(cfs_rq);
		u64 pair_slice = rq->clock - cfs_rq->pair_start;

		if (!cfs_rq->next \|\| pair_slice > sysctl_sched_min_granularity) {
		cfs_rq->pair_start = rq->clock;
		if (!cfs_rq->next \|\| wakeup_preempt_entity(cfs_rq->next, se) == 1)
		return se;
		}

		return cfs_rq->next;
		}

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