linux-kernel - Re: [PATCH -mm] cpuset,mm: fix no node to alloc memory when changing cpuset's mems

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Message-ID: <4BEA6E3D.10503@cn.fujitsu.com>
Date:	Wed, 12 May 2010 17:00:45 +0800
From:	Miao Xie <miaox@...fujitsu.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	David Rientjes <rientjes@...gle.com>,
	Lee Schermerhorn <lee.schermerhorn@...com>,
	Nick Piggin <npiggin@...e.de>, Paul Menage <menage@...gle.com>,
	Linux-Kernel <linux-kernel@...r.kernel.org>,
	Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH -mm] cpuset,mm: fix no node to alloc memory when changing
 cpuset's mems - fix2

on 2010-5-12 12:32, Andrew Morton wrote:
> On Wed, 12 May 2010 15:20:51 +0800 Miao Xie <miaox@...fujitsu.com> wrote:
> 
>> @@ -985,6 +984,7 @@ repeat:
>>  	 * for the read-side.
>>  	 */
>>  	while (ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
>> +		task_unlock(tsk);
>>  		if (!task_curr(tsk))
>>  			yield();
>>  		goto repeat;
> 
> Oh, I meant to mention that.  No yield()s, please.  Their duration is
> highly unpredictable.  Can we do something more deterministic here?

Maybe we can use wait_for_completion().

> 
> Did you consider doing all this with locking?  get_mems_allowed() does
> mutex_lock(current->lock)?

do you means using a real lock(such as: mutex) to protect mempolicy and mem_allowed?

It may cause the performance regression, so I do my best to abstain from using a real
lock.

Thanks
Miao

> 
> 
> 
> 


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