Re: [PATCH 2/6] sched/topology: optimize topology_span_sane()

[Christophe JAILLET]

Le 14/05/2024 à 00:01, Yury Norov a écrit :
> 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-Re5JQEeQqe8AvxtiuMwx3w@xxxxxxxxxxxxxxxx>
> ---
>   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

Hi,

does it make sense to pre-compute tl->mask(cpu) outside the for_each_cpu()?

CJ