CFS

#endif /* CONFIG_SMP */

/*
 * Update the current task's runtime statistics.
 */
static void update_curr(struct cfs_rq *cfs_rq)
{
	struct sched_entity *curr = cfs_rq->curr;
	u64 now = rq_clock_task(rq_of(cfs_rq));
	u64 delta_exec;

	if (unlikely(!curr))
		return;

	delta_exec = now - curr->exec_start;
	if (unlikely((s64)delta_exec <= 0))
		return;

	curr->exec_start = now;

	if (schedstat_enabled()) {
		struct sched_statistics *stats;

		stats = __schedstats_from_se(curr);
		__schedstat_set(stats->exec_max,
				max(delta_exec, stats->exec_max));
	}

	curr->sum_exec_runtime += delta_exec;
	schedstat_add(cfs_rq->exec_clock, delta_exec);

	curr->vruntime += calc_delta_fair(delta_exec, curr);
	update_deadline(cfs_rq, curr);
	update_min_vruntime(cfs_rq);

	if (entity_is_task(curr)) {
		struct task_struct *curtask = task_of(curr);

		trace_sched_stat_runtime(curtask, delta_exec, curr->vruntime);
		cgroup_account_cputime(curtask, delta_exec);

 * 2) pick the "next" process, since someone really wants that to run
 * 3) pick the "last" process, for cache locality
 * 4) do not run the "skip" process, if something else is available
 */
static struct sched_entity *
pick_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
	/*
	 * Enabling NEXT_BUDDY will affect latency but not fairness.
	 */
	if (sched_feat(NEXT_BUDDY) &&
	    cfs_rq->next && entity_eligible(cfs_rq, cfs_rq->next))
		return cfs_rq->next;

	return pick_eevdf(cfs_rq);
}

static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq);

static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
{
	/*
	 * If still on the runqueue then deactivate_task()
	 * was not called and update_curr() has to be done:
	 */
	if (prev->on_rq)
		update_curr(cfs_rq);

	/* throttle cfs_rqs exceeding runtime */
	check_cfs_rq_runtime(cfs_rq);

	if (prev->on_rq) {
		update_stats_wait_start_fair(cfs_rq, prev);
		/* Put 'current' back into the tree. */
		__enqueue_entity(cfs_rq, prev);
		/* in !on_rq case, update occurred at dequeue */
		update_load_avg(cfs_rq, prev, 0);
	}
	cfs_rq->curr = NULL;
}