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Date: Mon, 21 Aug 2006 15:02:17 +0400
From: Kirill Korotaev <dev@sw.ru>
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To: Matt Helsley <matthltc@us.ibm.com>
CC: "Chandra S. Seetharaman" <sekharan@us.ibm.com>,
       Rik van Riel <riel@redhat.com>,
       CKRM-Tech <ckrm-tech@lists.sourceforge.net>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andi Kleen <ak@suse.de>, Christoph Hellwig <hch@infradead.org>,
       Andrey Savochkin <saw@sw.ru>, devel@openvz.org, hugh@veritas.com,
       Ingo Molnar <mingo@elte.hu>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
       Pavel Emelianov <xemul@openvz.org>, Andrew Morton <akpm@osdl.org>
Subject: Re: [ckrm-tech] [RFC][PATCH 2/7] UBC: core (structures, API)
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>>>>+	for (p = ub; p != NULL; p = p->parent) {
>>>
>>>
>>>Seems rather expensive to walk up the tree for every charge. Especially
>>>if the administrator wants a fine degree of resource control and makes a
>>>tall tree. This would be a problem especially when it comes to resources
>>>that require frequent and fast allocation.
>>
>>in heirarchical accounting you always have to update all the nodes :/
>>with flat UBC this doesn't introduce significant overhead.
> 
> 
> Except that you eventually have to lock ub0. Seems that the cache line
> for that spinlock could bounce quite a bit in such a hot path.
do you mean by ub0 host system ub which we call ub0
or you mean a top ub?

> Chandra, doesn't Resource Groups avoid walking more than 1 level up the
> hierarchy in the "charge" paths?

Kirill