From: Yury Norov <yury.norov@gmail.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
Valentin Schneider <vschneid@redhat.com>,
linux-kernel@vger.kernel.org
Cc: Yury Norov <yury.norov@gmail.com>
Subject: [PATCH] sched: fair: drop useless cpumask_empty() in find_energy_efficient_cpu()
Date: Wed, 10 Sep 2025 22:34:25 -0400 [thread overview]
Message-ID: <20250911023426.457745-1-yury.norov@gmail.com> (raw)
From: Yury Norov (NVIDIA) <yury.norov@gmail.com>
cpumask_empty() call is O(N) and useless, because the previous
cpumask_and() returns false for empty 'cpus'.
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
---
kernel/sched/fair.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b173a059315c..7229339cbb1b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8320,9 +8320,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu)
int max_spare_cap_cpu = -1;
int fits, max_fits = -1;
- cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask);
-
- if (cpumask_empty(cpus))
+ if (!cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask))
continue;
/* Account external pressure for the energy estimation */
--
2.43.0
next reply other threads:[~2025-09-11 2:34 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-09-11 2:34 Yury Norov [this message]
2025-09-11 6:44 ` [PATCH] sched: fair: drop useless cpumask_empty() in find_energy_efficient_cpu() K Prateek Nayak
2025-09-11 6:45 ` Madadi Vineeth Reddy
2025-09-11 8:28 ` Vincent Guittot
2025-09-11 14:00 ` Markus Elfring
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