linux-kernel - Re: [ckrm-tech] [PATCH 5/13] BC: user interface (syscalls)

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Date:	Wed, 06 Sep 2006 14:27:38 +0530
From:	Balbir Singh <balbir@...ibm.com>
To:	Pavel Emelianov <xemul@...nvz.org>
Cc:	Kirill Korotaev <dev@...ru>, Andrew Morton <akpm@...l.org>,
	Rik van Riel <riel@...hat.com>,
	CKRM-Tech <ckrm-tech@...ts.sourceforge.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andi Kleen <ak@...e.de>, Christoph Hellwig <hch@...radead.org>,
	Andrey Savochkin <saw@...ru>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Hugh Dickins <hugh@...itas.com>,
	Matt Helsley <matthltc@...ibm.com>,
	Alexey Dobriyan <adobriyan@...l.ru>,
	Oleg Nesterov <oleg@...sign.ru>, devel@...nvz.org
Subject: Re: [ckrm-tech] [PATCH 5/13] BC: user interface (syscalls)

Pavel Emelianov wrote:
> Balbir Singh wrote:
>>> +
>>> +asmlinkage long sys_set_bcid(bcid_t id)
>>> +{
>>> +    int error;
>>> +    struct beancounter *bc;
>>> +    struct task_beancounter *task_bc;
>>> +
>>> +    task_bc = &current->task_bc;
>> I was playing around with the bc patches and found that to make
>> use of bc's, I had to actually call set_bcid() and then exec() a
>> task/shell so that the id would stick around. Would you consider
> That sounds very strange as sys_set_bcid() actually changes current's
> exec_bc.
> One note is about mm's bc - mm obtains new bc only after fork or exec -
> that's
> true. But kmemsize starts charging right after the sys_set_bcid.

I was playing around only with kmemsize. I think the reason for my observation
is this

bash --> (my utility) --> set_bcid()

Since bash spawns my utility in a separate process, it creates and assigns
a bean counter to it and then my utility exits. Unless it spawns/exec()'s a
new shell, the beancounter is freed when the task exits (my utility).

>> changing sys_set_bcid to sys_set_task_bcid() or adding a new
>> system call sys_set_task_bcid()? We could pass the pid that we
>> intend to associate with the new id. This also means we'll need
>> locking around to protect task->task_bc.
> 


-- 

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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