linux-kernel - Re: [ckrm-tech] [RFC][PATCH 6/8] RSS controller shares allocation

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Message-ID: <455476C0.6010204@in.ibm.com>
Date:	Fri, 10 Nov 2006 18:25:28 +0530
From:	Balbir Singh <balbir@...ibm.com>
To:	Pavel Emelianov <xemul@...nvz.org>
CC:	dev@...nvz.org, ckrm-tech@...ts.sourceforge.net,
	haveblue@...ibm.com,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, rohitseth@...gle.com
Subject: Re: [ckrm-tech] [RFC][PATCH 6/8] RSS controller shares allocation

Pavel Emelianov wrote:
> [snip]
> 
>>>> +	for_each_child(child, res->rgroup) {
>>>> +		child_res = get_memctlr(child);
>>>> +		BUG_ON(!child_res);
>>>> +		recalc_and_propagate(child_res, res);
>>> Recursion? Won't it eat all the stack in case of a deep tree?
>> The depth of the hierarchy can be controlled. Recursion is needed
>> to do a DFS walk
> 
> That's another point against recursion - bad root can
> crash the kernel... If we are about to give container's
> users ability to make their own subtrees then we *must*
> avoid recursion. There's an algorithm that allows one
> to walk the tree like this w/o recursion.

Bad pointers are always bad, whether they are the root or
any other pointer. Tree traversal is a generic infrastructure issue
for any infrastructure that supports a hierarchy.

Are you talking about threaded trees? Yes, they can be traversed
without recursion. I need to recheck my DS reference to double
check.

> 
> [snip]
> 
>>> I didn't find where in this patches this callback is called.
>> It's a part of the resource groups infrastructure. It's been ported
>> on top of Paul Menage's containers patches. The code can be easily
>> adapted to work directly with containers instead of resource groups
>> if required.
> 
> 
> Could you please give me a link to the patch where this
> is called?

Please see

http://www.mail-archive.com/ckrm-tech@lists.sourceforge.net/msg03333.html

-- 

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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