Re: [RFC PATCH] sched: Add scx_cpuperf_target in sched_cpu_util()

[Peter Zijlstra]

On Wed, Mar 18, 2026 at 08:17:55PM +0800, Xuewen Yan wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index bf948db905ed..20adb6fede2a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -8198,7 +8198,12 @@ unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
>  
>  unsigned long sched_cpu_util(int cpu)
>  {
> -	return effective_cpu_util(cpu, cpu_util_cfs(cpu), NULL, NULL);
> +	unsigned long util = scx_cpuperf_target(cpu);
> +
> +	if (!scx_switched_all())
> +		util += cpu_util_cfs(cpu);
> +
> +	return effective_cpu_util(cpu, util, NULL, NULL);
>  }

This puts the common case of no ext muck into the slow path of that
static_branch.

This wants to be something like:

unsigned long sched_cpu_util(int cpu)
{
	unsigned long util = cpu_util_cfs(cpu);

	if (scx_enabled()) {
		unsigned long scx_util = scx_cpuperf_target(cpu);

		if (!scx_switched_all())
			scx_util += util;

		util = scx_util;
	}

	return effective_cpu_util(cpu, util, NULL, NULL);
}