Re: [PATCH 2/6] sched/numa: fix scan-period ratio denominator checks

[Gregory Price <gourry@gourry.net>]

On Wed, Oct 14, 2026 at 05:43:43PM +0800, Li Zhe wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1053437933ee..76532b8202dc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -3698,6 +3698,8 @@ static void update_task_scan_period(struct task_struct *p,
>  
>  	unsigned long remote = p->numa_faults_locality[0];
>  	unsigned long local = p->numa_faults_locality[1];
> +	unsigned long locality_faults = local + remote;
> +	unsigned long type_faults = private + shared;
>  
>  	/*
>  	 * If there were no record hinting faults then either the task is
> @@ -3706,7 +3708,7 @@ static void update_task_scan_period(struct task_struct *p,
>  	 * migration then it implies we are migrating too quickly or the local
>  	 * node is overloaded. In either case, scan slower
>  	 */
> -	if (local + shared == 0 || p->numa_faults_locality[2]) {
> +	if (!locality_faults || !type_faults || p->numa_faults_locality[2]) {
>  		p->numa_scan_period = min(p->numa_scan_period_max,
>  			p->numa_scan_period << 1);
> 

This does more than just change the div/o below, it changes the behavior
of the function overall.  It's not clear to me this change is correct.

> @@ -3723,8 +3725,8 @@ static void update_task_scan_period(struct task_struct *p,
>  	 *	 >= NUMA_PERIOD_THRESHOLD scan period increases (scan slower)
>  	 */
>  	period_slot = DIV_ROUND_UP(p->numa_scan_period, NUMA_PERIOD_SLOTS);
> -	lr_ratio = (local * NUMA_PERIOD_SLOTS) / (local + remote);
> -	ps_ratio = (private * NUMA_PERIOD_SLOTS) / (private + shared);
> +	lr_ratio = (local * NUMA_PERIOD_SLOTS) / locality_faults;
> +	ps_ratio = (private * NUMA_PERIOD_SLOTS) / type_faults;
>  

This otherwise looks fine.

~Gregory