linux-kernel - Re: [PATCH] cpuset: fix allocating page cache/slab object on the unallowed node when memory spread is set

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Message-Id: <20090127144233.18cf9b3f.akpm@linux-foundation.org>
Date:	Tue, 27 Jan 2009 14:42:33 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	miaox@...fujitsu.com
Cc:	mingo@...e.hu, menage@...gle.com, linux-kernel@...r.kernel.org,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <nickpiggin@...oo.com.au>
Subject: Re: [PATCH] cpuset: fix allocating page cache/slab object on the
 unallowed node when memory spread is set

On Wed, 21 Jan 2009 16:06:20 +0800
Miao Xie <miaox@...fujitsu.com> wrote:

> The task still allocated the page caches on old node after modifying its
> cpuset's mems when 'memory_spread_page' was set, it is caused by the old
> mem_allowed_list of the task, the current kernel doesn't updates it unless some
> function invokes cpuset_update_task_memory_state(), it is too late sometimes.
> We must update the mem_allowed_list of the tasks in time.
> 
> Slab has the same problem.
> 
> We fixes the bug by updating tasks' mem_allowed_list and spread flag after
> its cpuset's mems or spread flag is changed.
> 
>
> ...
>
> --- a/kernel/kthread.c
> +++ b/kernel/kthread.c
> @@ -242,6 +242,7 @@ int kthreadd(void *unused)
>  	set_user_nice(tsk, KTHREAD_NICE_LEVEL);
>  	set_cpus_allowed_ptr(tsk, CPU_MASK_ALL_PTR);
>  
> +	current->mems_allowed = node_possible_map;
>  	current->flags |= PF_NOFREEZE | PF_FREEZER_NOSIG;

Why this change?  kthreadd() is called from rest_init(), before anyone
has had a chance to alter ->mems_allowed?


I queued the patch pending your response to Paul's questions, thanks.
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