linux-kernel - [PATCH v3 1/3] sched/topology: pre-compute topology_span

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20240902183609.1683756-2-yury.norov@gmail.com>
Date: Mon,  2 Sep 2024 11:36:05 -0700
From: Yury Norov <yury.norov@...il.com>
To: linux-kernel@...r.kernel.org,
	Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: Yury Norov <yury.norov@...il.com>,
	Chen Yu <yu.c.chen@...el.com>,
	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 v3 1/3] sched/topology: pre-compute topology_span_sane() loop params

tl->mask() is called inside the loop with the same parameters more than
once. We can pre-calculate it. After that, 'cpu' doesn't have to keep its
value while running the loop iterations. We can drop the 'i' iterator,
and re-use 'cpu' in the for_each_cpu_from() loop.

Reviewed-by: Chen Yu <yu.c.chen@...el.com>
Signed-off-by: Yury Norov <yury.norov@...il.com>
---
 kernel/sched/topology.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 76504b776d03..ffbe3a28d2d4 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2353,27 +2353,30 @@ 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)
 {
-	int i = cpu + 1;
+	const struct cpumask *mi, *mc;
 
 	/* NUMA levels are allowed to overlap */
 	if (tl->flags & SDTL_OVERLAP)
 		return true;
 
+	mc = tl->mask(cpu++);
+
 	/*
 	 * Non-NUMA levels cannot partially overlap - they must be either
 	 * completely equal or completely disjoint. Otherwise we can end up
 	 * breaking the sched_group lists - i.e. a later get_group() pass
 	 * breaks the linking done for an earlier span.
 	 */
-	for_each_cpu_from(i, cpu_map) {
+	for_each_cpu_from(cpu, cpu_map) {
+		mi = tl->mask(cpu);
+
 		/*
 		 * 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