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sched/topology: Optimize topology_span_sane() 

Optimize topology_span_sane() by removing duplicate comparisons.

Since topology_span_sane() is called inside of for_each_cpu(), each
previous CPU has already been compared against every other CPU. The
current CPU only needs to be compared against higher-numbered CPUs.

The total number of comparisons is reduced from N * (N - 1) to
N * (N - 1) / 2 on each non-NUMA scheduling domain level.

Signed-off-by: Kyle Meyer <kyle.meyer@hpe.com>
Reviewed-by: Yury Norov <yury.norov@gmail.com>
Acked-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Yury Norov <yury.norov@gmail.com>
This commit is contained in:
Kyle Meyer 2024-04-10 16:33:11 -05:00 committed by Yury Norov
parent 6802f93479
commit 05037e5f0f
1 changed files with 2 additions and 4 deletions
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6
kernel/sched/topology.c
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@ -2347,7 +2347,7 @@ 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)
{
int i;
int i = cpu + 1;
/* NUMA levels are allowed to overlap */
if (tl->flags & SDTL_OVERLAP)
@ -2359,9 +2359,7 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl,
* breaking the sched_group lists - i.e. a later get_group() pass
* breaks the linking done for an earlier span.
*/
for_each_cpu(i, cpu_map) {
if (i == cpu)
continue;
for_each_cpu_from(i, cpu_map) {
/*
* We should 'and' all those masks with 'cpu_map' to exactly
* match the topology we're about to build, but that can only