[tip: sched/core] sched/core: Optimize core cookie matching check

["tip-bot2 for Fernand Sieber" <tip-bot2@linutronix.de>]

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     7f829bde94b1c97b1804fa5860e066ea49dbfca3
Gitweb:        https://git.kernel.org/tip/7f829bde94b1c97b1804fa5860e066ea49dbfca3
Author:        Fernand Sieber <sieberf@amazon.com>
AuthorDate:    Wed, 05 Nov 2025 17:25:37 +02:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 11 Nov 2025 12:33:37 +01:00

sched/core: Optimize core cookie matching check

Early return true if the core cookie matches. This avoids the SMT mask
loop to check for an idle core, which might be more expensive on wide
platforms.

Signed-off-by: Fernand Sieber <sieberf@amazon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Madadi Vineeth Reddy <vineethr@linux.ibm.com>
Link: https://patch.msgid.link/20251105152538.470586-1-sieberf@amazon.com
---
 kernel/sched/sched.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index d04e007..82e74e8 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1432,6 +1432,9 @@ static inline bool sched_core_cookie_match(struct rq *rq, struct task_struct *p)
 	if (!sched_core_enabled(rq))
 		return true;
 
+	if (rq->core->core_cookie == p->core_cookie)
+		return true;
+
 	for_each_cpu(cpu, cpu_smt_mask(cpu_of(rq))) {
 		if (!available_idle_cpu(cpu)) {
 			idle_core = false;
@@ -1443,7 +1446,7 @@ static inline bool sched_core_cookie_match(struct rq *rq, struct task_struct *p)
 	 * A CPU in an idle core is always the best choice for tasks with
 	 * cookies.
 	 */
-	return idle_core || rq->core->core_cookie == p->core_cookie;
+	return idle_core;
 }
 
 static inline bool sched_group_cookie_match(struct rq *rq,