Re: [PATCH v3 1/5] sched/deadline: Optimize dl_bw_cpus()

Juri Lelli
2020-05-22T14:57:29Z

On 20/05/20 15:42, Dietmar Eggemann wrote:
> Return the weight of the root domain (rd) span in case it is a subset
> of the cpu_active_mask.
>
> Continue to compute the number of CPUs over rd span and cpu_active_mask
> when in hotplug.
>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
> ---
> kernel/sched/deadline.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 504d2f51b0d6..4ae22bfc37ae 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -54,10 +54,16 @@ static inline struct dl_bw *dl_bw_of(int i)
> static inline int dl_bw_cpus(int i)
> {
> struct root_domain *rd = cpu_rq(i)->rd;
> - int cpus = 0;
> + int cpus;
>
> RCU_LOCKDEP_WARN(!rcu_read_lock_sched_held(),
> "sched RCU must be held");
> +
> + if (cpumask_subset(rd->span, cpu_active_mask))
> + return cpumask_weight(rd->span);
> +
> + cpus = 0;
> +
> for_each_cpu_and(i, rd->span, cpu_active_mask)
> cpus++;
>
> --