Commit 37341ec5 authored by John Stultz's avatar John Stultz Committed by Peter Zijlstra
Browse files

sched: Minimise repeated sched_proxy_exec() checking 



Peter noted: Compilers are really bad (as in they utterly refuse)
optimizing (even when marked with __pure) the static branch
things, and will happily emit multiple identical in a row.

So pull out the one obvious sched_proxy_exec() branch in
__schedule() and remove some of the 'implicit' ones in that
path.

Suggested-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarJohn Stultz <jstultz@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260324191337.1841376-3-jstultz@google.com
parent e0ca8991

kernel/sched/core.c

+9 −11
Original line number Diff line number Diff line
@@ -6597,11 +6597,7 @@ find_proxy_task(struct rq *rq, struct task_struct *donor, struct rq_flags *rf) 
	struct mutex *mutex;



	/* Follow blocked_on chain. */

	for (p = donor; task_is_blocked(p); p = owner) {

		mutex = p->blocked_on;

		/* Something changed in the chain, so pick again */

		if (!mutex)

			return NULL;

	for (p = donor; (mutex = p->blocked_on); p = owner) {

		/*

		 * By taking mutex->wait_lock we hold off concurrent mutex_unlock()

		 * and ensure @owner sticks around.
@@ -6832,13 +6828,15 @@ static void __sched notrace __schedule(int sched_mode) 
	next = pick_next_task(rq, rq->donor, &rf);

	rq_set_donor(rq, next);

	rq->next_class = next->sched_class;

	if (unlikely(task_is_blocked(next))) {

	if (sched_proxy_exec()) {

		if (unlikely(next->blocked_on)) {

			next = find_proxy_task(rq, next, &rf);

			if (!next)

				goto pick_again;

			if (next == rq->idle)

				goto keep_resched;

		}

	}

picked:

	clear_tsk_need_resched(prev);

	clear_preempt_need_resched();