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sched: Minimise repeated sched_proxy_exec() checking

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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: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Link: https://patch.msgid.link/20260324191337.1841376-3-jstultz@google.com
This commit is contained in:
John Stultz 2026-03-24 19:13:17 +00:00 committed by Peter Zijlstra
parent e0ca8991b2
commit 37341ec573
1 changed files with 9 additions and 11 deletions
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20
kernel/sched/core.c
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@ -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.
@ -6832,12 +6828,14 @@ 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))) {
next = find_proxy_task(rq, next, &rf);
if (!next)
goto pick_again;
if (next == rq->idle)
goto keep_resched;
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);