Re: [PATCH v5 07/24] sched/fair: Select preferred CPU at wakeup when possible

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Jun 25, 2026 at 06:16:31PM +0530, Shrikanth Hegde wrote:
> Update available_idle_cpu to consider preferred CPUs. This takes care of
> lot of decisions at wakeup to use only preferred CPUs. There is no need to
> put those explicit checks everywhere.
> 
> Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
> ---
>  kernel/sched/sched.h | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 5d009c2529b2..148fe6145f1a 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1434,6 +1434,9 @@ static inline bool available_idle_cpu(int cpu)
>  	if (!idle_rq(cpu_rq(cpu)))
>  		return 0;
>  
> +	if (!cpu_preferred(cpu))
> +		return 0;
> +
>  	if (vcpu_is_preempted(cpu))
>  		return 0;
>  

This one might hurt, it is a whole extra cacheline in otherwise already
sensitive (wakeup) paths.