Messages in this thread Patch in this message | | | From | Kyle Meyer <> | Subject | [PATCH v2 2/2] sched/topology: Optimize topology_span_sane() | Date | Wed, 10 Apr 2024 16:33:11 -0500 |
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Optimize topology_span_sane() by removing duplicate comparisons.
Since topology_span_sane() is called inside of for_each_cpu(), each pervious 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> --- kernel/sched/topology.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 99ea5986038c..b6bcafc09969 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -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 -- 2.44.0
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