Re: [PATCH 1/4] sched/rt: Optimize cpupri_vec layout to mitigate cache line contention

["Chen, Yu C" <yu.c.chen@intel.com>]

On 7/7/2025 10:35 AM, Pan Deng wrote:
> When running a multi-instance FFmpeg workload on an HCC system, significant
> cache line contention is observed around `cpupri_vec->count` and `mask` in
> struct root_domain.
> 

[it seems that my last reply did not make it to the lkml][snip]

> diff --git a/kernel/sched/cpupri.h b/kernel/sched/cpupri.h
> index d6cba0020064..245b0fa626be 100644
> --- a/kernel/sched/cpupri.h
> +++ b/kernel/sched/cpupri.h
> @@ -9,7 +9,7 @@
>   
>   struct cpupri_vec {
>   	atomic_t		count;
> -	cpumask_var_t		mask;
> +	cpumask_var_t		mask	____cacheline_aligned;

Just curious, since this is to avoid cache contention among CPUs,
is it better to use ____cacheline_aligned_in_smp, so the single
CPU system is not impacted.

thanks,
Chenyu>   };
>   
>   struct cpupri {