linux-kernel - Re: [PATCH v2 1/3] sched/fair: Remove unused task_numa

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Message-ID: <d6ef6cb3-fee6-4ab7-a2ed-33139295a3c5@linux.ibm.com>
Date: Sun, 5 Jan 2025 23:58:07 +0530
From: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
To: Chuyi Zhou <zhouchuyi@...edance.com>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        vschneid@...hat.com, longman@...hat.com, riel@...riel.com,
        chengming.zhou@...ux.dev, kprateek.nayak@....com,
        linux-kernel@...r.kernel.org,
        Madadi Vineeth Reddy <vineethr@...ux.ibm.com>
Subject: Re: [PATCH v2 1/3] sched/fair: Remove unused task_numa_migrate return
 value

Hi Chuyi Zhou,

On 03/01/25 12:29, Chuyi Zhou wrote:
> Initial NUMA Balancing implementation used the return value of
> task_numa_migrate() to retry NUMA Balancing in commit 6b9a7460b6ba
> ("sched/numa: Retry migration of tasks to CPU on a preferred node") however
> in the same series[1], Mel also included an optimization from Rik which
> retried NUMA Balancing periodically irrespective the return value from
> task_numa_migrate() in commit 2739d3eef3a9 ("sched/numa: Retry
> task_numa_migrate() periodically").

Maybe you can also add: 
Fixes: 2739d3eef3a9 ("sched/numa: Retry task_numa_migrate() periodically")
While it's not strictly required, it might be useful to include for context.
> 
> The return value of task_numa_migrate now is unused, remove it.

Yes, it's unused now.
Reviewed-by: Madadi Vineeth Reddy <vineethr@...ux.ibm.com>

Thanks,
Madadi Vineeth Reddy

> 
> [1] https://lore.kernel.org/all/1381141781-10992-34-git-send-email-mgorman@suse.de/
> 
> Reviewed-by: K Prateek Nayak <kprateek.nayak@....com>
> Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>
> ---
>  kernel/sched/fair.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index d5127d9beaea..f544012b9320 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2486,7 +2486,7 @@ static void task_numa_find_cpu(struct task_numa_env *env,
>  	}
>  }
>  
> -static int task_numa_migrate(struct task_struct *p)
> +static void task_numa_migrate(struct task_struct *p)
>  {
>  	struct task_numa_env env = {
>  		.p = p,
> @@ -2531,7 +2531,7 @@ static int task_numa_migrate(struct task_struct *p)
>  	 */
>  	if (unlikely(!sd)) {
>  		sched_setnuma(p, task_node(p));
> -		return -EINVAL;
> +		return;
>  	}
>  
>  	env.dst_nid = p->numa_preferred_nid;
> @@ -2600,7 +2600,7 @@ static int task_numa_migrate(struct task_struct *p)
>  	/* No better CPU than the current one was found. */
>  	if (env.best_cpu == -1) {
>  		trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
> -		return -EAGAIN;
> +		return;
>  	}
>  
>  	best_rq = cpu_rq(env.best_cpu);
> @@ -2609,7 +2609,7 @@ static int task_numa_migrate(struct task_struct *p)
>  		WRITE_ONCE(best_rq->numa_migrate_on, 0);
>  		if (ret != 0)
>  			trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
> -		return ret;
> +		return;
>  	}
>  
>  	ret = migrate_swap(p, env.best_task, env.best_cpu, env.src_cpu);
> @@ -2618,7 +2618,6 @@ static int task_numa_migrate(struct task_struct *p)
>  	if (ret != 0)
>  		trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
>  	put_task_struct(env.best_task);
> -	return ret;
>  }
>  
>  /* Attempt to migrate a task to a CPU on the preferred node. */