linux-kernel - Re: [PATCH] sched/fair: simplify task_numa_find

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Message-ID: <20250911212054.GD7235@pauld.westford.csb>
Date: Thu, 11 Sep 2025 17:20:54 -0400
From: Phil Auld <pauld@...hat.com>
To: Yury Norov <yury.norov@...il.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: simplify task_numa_find_cpu()

On Thu, Sep 11, 2025 at 04:31:35PM -0400 Yury Norov wrote:
> From: Yury Norov (NVIDIA) <yury.norov@...il.com>
> 
> Use for_each_cpu_and() and drop some housekeeping code.
> 
> Signed-off-by: Yury Norov (NVIDIA) <yury.norov@...il.com>

The "housekeeping" part threw me off for a second. I was looking for
isolation related code being dropped :)


Reviewed-by: Phil Auld <pauld@...hat.com>


> ---
>  kernel/sched/fair.c | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 0990ed90c14e..c48c0975fe7a 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2474,11 +2474,8 @@ static void task_numa_find_cpu(struct task_numa_env *env,
>  		maymove = !load_too_imbalanced(src_load, dst_load, env);
>  	}
>  
> -	for_each_cpu(cpu, cpumask_of_node(env->dst_nid)) {
> -		/* Skip this CPU if the source task cannot migrate */
> -		if (!cpumask_test_cpu(cpu, env->p->cpus_ptr))
> -			continue;
> -
> +	/* Skip CPUs if the source task cannot migrate */
> +	for_each_cpu_and(cpu, cpumask_of_node(env->dst_nid), env->p->cpus_ptr) {
>  		env->dst_cpu = cpu;
>  		if (task_numa_compare(env, taskimp, groupimp, maymove))
>  			break;
> -- 
> 2.43.0
> 
> 

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