linux-kernel - Re: [ckrm-tech] [PATCH 4/13] BC: context handling

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Message-ID: <456AA17D.9020205@openvz.org>
Date:	Mon, 27 Nov 2006 11:27:41 +0300
From:	Pavel Emelianov <xemul@...nvz.org>
To:	Paul Menage <menage@...gle.com>
CC:	Kirill Korotaev <dev@...ru>, Andrew Morton <akpm@...l.org>,
	ckrm-tech@...ts.sourceforge.net,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	matthltc@...ibm.com, hch@...radead.org,
	Alan Cox <alan@...rguk.ukuu.org.uk>, oleg@...sign.ru,
	devel@...nvz.org
Subject: Re: [ckrm-tech] [PATCH 4/13] BC: context handling

Paul Menage wrote:
> On 11/24/06, Pavel Emelianov <xemul@...nvz.org> wrote:
>> I've got it! That's what will work:
>>
>> struct task_struct {
>>         ...
>>         struct beancounter *exec_bc;
>>         struct beancounter *tmp_exec_bc; /* is set to NULL on
>>                                           * tsk creation
>>                                           */
>> };
>>
>> struct beancounter get_exec_bc(void)
>> {
>>         if (current->tmp_exec_bc)
>>                 return current->tmp_exec_bc;
>>         return rcu_dereference(current->exec_bc);
>> }
> 
> Don't forget that this means all callers need to be in an
> rcu_read_lock() section.

Sure. This is done for these particular cases.

>>
>> I will implement this in the next beancounter patches.
> 
> This is looking remarkably like the mechanism in use for my generic
> containers patches (inherited from Paul Jackson's cpusets code). In
> the last set of patches that I posted on Wednesday night, I included
> the example of the beancounters core and numfiles counter implemented
> on top of the generic containers - basically pulling out the hash
> table, refcounting and most of the configfs code (since that's handled
> by the generic containers), and moving the attribute management
> configfs code to the use the containerfs filesystem interface instead.
> The rest is pretty much unchanged.
> 
> I think you could continue to use the tmp_exec_bc idea with this, and
> have get_exec_bc() use the tmp_exec_bc if it existed, or else get the
> bc pointer via the container system.

I'll look through your patches this week and send my opinion.

> I'd appreciate any feedback you had on that approach.
> 
> Paul

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