linux-kernel - Re: [PATCH 4/8] sched: clean up move_task() and move_one

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Date:	Tue, 19 Mar 2013 15:30:15 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/8] sched: clean up move_task() and move_one_task()

On Thu, 2013-02-14 at 14:48 +0900, Joonsoo Kim wrote:
> Some validation for task moving is performed in move_tasks() and
> move_one_task(). We can move these code to can_migrate_task()
> which is already exist for this purpose.

> @@ -4011,18 +4027,7 @@ static int move_tasks(struct lb_env *env)
>  			break;
>  		}
>  
> -		if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
> -			goto next;
> -
> -		load = task_h_load(p);
> -
> -		if (sched_feat(LB_MIN) && load < 16 && !env->sd->nr_balance_failed)
> -			goto next;
> -
> -		if ((load / 2) > env->imbalance)
> -			goto next;
> -
> -		if (!can_migrate_task(p, env))
> +		if (!can_migrate_task(p, env, false, &load))
>  			goto next;
>  
>  		move_task(p, env);

Right, so I'm not so taken with this one. The whole load stuff really
is a balance heuristic that's part of move_tasks(), move_one_task()
really doesn't care about that.

So why did you include it? Purely so you didn't have to re-order the
tests? I don't see any reason not to flip a tests around.

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