linux-kernel - Re: [rfc] balance-on-fork NUMA placement

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Date:	Tue, 31 Jul 2007 10:01:14 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Nick Piggin <npiggin@...e.de>
Cc:	Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [rfc] balance-on-fork NUMA placement


* Nick Piggin <npiggin@...e.de> wrote:

> This patch uses memory policies to attempt to improve this. It 
> requires that we ask the scheduler to suggest the child's new CPU 
> earlier in the fork, but that is not a fundamental difference.

no fundamental objections, but i think we could simply move sched_fork() 
to the following place:

> @@ -989,10 +990,13 @@ static struct task_struct *copy_process(
>  	if (retval)
>  		goto fork_out;
>  
> +	cpu = sched_fork_suggest_cpu(clone_flags);
> +	mpol_arg = mpol_prefer_cpu_start(cpu);
> +
>  	retval = -ENOMEM;
>  	p = dup_task_struct(current);
>  	if (!p)
> -		goto fork_out;
> +		goto fork_mpol;
>  
>  	rt_mutex_init_task(p);


_after_ the dup_task_struct(). Then change sched_fork() to return a CPU 
number - hence we dont have a separate sched_fork_suggest_cpu() 
initialization function, only one, obvious sched_fork() function. 
Agreed?

	Ingo
-
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