linux-kernel - [PATCH 1/2] sched/topology: pre-compute topology_span

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Message-ID: <20240802175750.1152788-2-yury.norov@gmail.com>
Date: Fri,  2 Aug 2024 10:57:42 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Yury Norov <yury.norov@...il.com>,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	Leonardo Bras <leobras@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>,
	Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>
Subject: [PATCH 1/2] sched/topology: pre-compute topology_span_sane() loop params

tl->mask(cpu) is used unchanged in the loop, and tl->mask(i) in worst
case may be calculated twice as parameters for cpumask_equal() and
cpumask_intersects(). So, precalculate both.

Suggested-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Suggested-by: Leonardo Bras <leobras@...hat.com>
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/sched/topology.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 76504b776d03..754ad5fa3c99 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2353,6 +2353,7 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve
 static bool topology_span_sane(struct sched_domain_topology_level *tl,
 			      const struct cpumask *cpu_map, int cpu)
 {
+	const struct cpumask *mi, *mc = tl->mask(cpu);
 	int i = cpu + 1;
 
 	/* NUMA levels are allowed to overlap */
@@ -2366,14 +2367,15 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl,
 	 * breaks the linking done for an earlier span.
 	 */
 	for_each_cpu_from(i, cpu_map) {
+		mi = tl->mask(i);
+
 		/*
 		 * We should 'and' all those masks with 'cpu_map' to exactly
 		 * match the topology we're about to build, but that can only
 		 * remove CPUs, which only lessens our ability to detect
 		 * overlaps
 		 */
-		if (!cpumask_equal(tl->mask(cpu), tl->mask(i)) &&
-		    cpumask_intersects(tl->mask(cpu), tl->mask(i)))
+		if (!cpumask_equal(mc, mi) && cpumask_intersects(mc, mi))
 			return false;
 	}
 
-- 
2.43.0