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

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Message-ID: <2bda56c3-727f-4899-8d88-fd83f11b3e76@amd.com>
Date: Wed, 18 Dec 2024 11:59:19 +0530
From: K Prateek Nayak <kprateek.nayak@....com>
To: Chuyi Zhou <zhouchuyi@...edance.com>, <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>
CC: <chengming.zhou@...ux.dev>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] sched/fair: Remove unused task_numa_migrate return
 value

Hello Chuyi,

On 12/16/2024 5:53 PM, Chuyi Zhou wrote:
> The return value of task_numa_migrate is unused, remove it.
> 
> Signed-off-by: Chuyi Zhou <zhouchuyi@...edance.com>

Feel free to include:

Reviewed-by: K Prateek Nayak <kprateek.nayak@....com>

If anyone cares for the history, 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")

[1] https://lore.kernel.org/all/1381141781-10992-34-git-send-email-mgorman@suse.de/

-- 
Thanks and Regards,
Prateek

> ---
>   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. */