linux-kernel - [PATCH 2/6] sched/topology: optimize topology_span

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Message-Id: <20240513220146.1461457-3-yury.norov@gmail.com>
Date: Mon, 13 May 2024 15:01:42 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Anna-Maria Behnsen <anna-maria@...utronix.de>,
	Ben Segall <bsegall@...gle.com>,
	Daniel Bristot de Oliveira <bristot@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Imran Khan <imran.f.khan@...cle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Leonardo Bras <leobras@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Rik van Riel <riel@...riel.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tejun Heo <tj@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Waiman Long <longman@...hat.com>,
	Yury Norov <yury.norov@...il.com>,
	Zefan Li <lizefan.x@...edance.com>,
	cgroups@...r.kernel.org
Subject: [PATCH 2/6] sched/topology: optimize topology_span_sane()

The function may call cpumask_equal with tl->mask(cpu) == tl->mask(i),
even though cpu != i. In such case, cpumask_equal() would always return
true, and we can proceed to the next CPU immediately.

Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/sched/topology.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 99ea5986038c..eb9eb17b0efa 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2360,7 +2360,7 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl,
 	 * breaks the linking done for an earlier span.
 	 */
 	for_each_cpu(i, cpu_map) {
-		if (i == cpu)
+		if (i == cpu || tl->mask(cpu) == tl->mask(i))
 			continue;
 		/*
 		 * We should 'and' all those masks with 'cpu_map' to exactly
-- 
2.40.1