sched: add avg_overlap decay (df1c99d4) · Commits · 戴 / test

Impact: more precise avg_overlap metric - better load-balancing avg_overlap is used to measure the runtime overlap of the waker and wakee. However, when a process changes behaviour, eg a pipe becomes un-congested and we don't need to go to sleep after a wakeup for a while, the avg_overlap value grows stale. When running we use the avg runtime between preemption as a measure for avg_overlap since the amount of runtime can be correlated to cache footprint. The longer we run, the less likely we'll be wanting to be migrated to another CPU. Signed-off-by:

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

Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1236709131.25234.576.camel@laptop> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+23 −1

Original line number	Diff line number	Diff line
		@@ -4620,6 +4620,28 @@ static inline void schedule_debug(struct task_struct *prev)
		#endif
		}

		static void put_prev_task(struct rq rq, struct task_struct prev)
		{
		if (prev->state == TASK_RUNNING) {
		u64 runtime = prev->se.sum_exec_runtime;

		runtime -= prev->se.prev_sum_exec_runtime;
		runtime = min_t(u64, runtime, 2*sysctl_sched_migration_cost);

		/*
		* In order to avoid avg_overlap growing stale when we are
		* indeed overlapping and hence not getting put to sleep, grow
		* the avg_overlap on preemption.
		*
		* We use the average preemption runtime because that
		* correlates to the amount of cache footprint a task can
		* build up.
		*/
		update_avg(&prev->se.avg_overlap, runtime);
		}
		prev->sched_class->put_prev_task(rq, prev);
		}

		/*
		* Pick up the highest-prio task:
		*/
		@@ -4698,7 +4720,7 @@ need_resched_nonpreemptible:
		if (unlikely(!rq->nr_running))
		idle_balance(cpu, rq);

		prev->sched_class->put_prev_task(rq, prev);
		put_prev_task(rq, prev);
		next = pick_next_task(rq);

		if (likely(prev != next)) {

Admin message