Re: [PATCH 2/4] sched/fair: Small cleanup to sched_balance_newidle()

[Shrikanth Hegde]

On 11/7/25 9:36 PM, Peter Zijlstra wrote:
> Pull out the !sd check to simplify code.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> ---
>   kernel/sched/fair.c |   10 ++++++----
>   1 file changed, 6 insertions(+), 4 deletions(-)
>
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -12811,14 +12811,16 @@ static int sched_balance_newidle(struct
>   
>   	rcu_read_lock();
>   	sd = rcu_dereference_check_sched_domain(this_rq->sd);
> +	if (!sd) {
> +		rcu_read_unlock();
> +		goto out;
> +	}
>   

when is sd null? on isol_cpus ?

if sd is null, i think we are skipping these compared to earlier.

        t0 = sched_clock_cpu(this_cpu);
        sched_balance_update_blocked_averages(this_cpu);

>   	if (!get_rd_overloaded(this_rq->rd) ||
> -	    (sd && this_rq->avg_idle < sd->max_newidle_lb_cost)) {
> +	    this_rq->avg_idle < sd->max_newidle_lb_cost) {
>   
> -		if (sd)
> -			update_next_balance(sd, &next_balance);
> +		update_next_balance(sd, &next_balance);
>   		rcu_read_unlock();
> -
>   		goto out;
>   	}
>   	rcu_read_unlock();