linux-kernel - Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added user memory)

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Date:	Mon, 11 Sep 2006 12:13:59 +0400
From:	Pavel Emelianov <xemul@...nvz.org>
To:	balbir@...ibm.com
CC:	Dave Hansen <haveblue@...ibm.com>, Rik van Riel <riel@...hat.com>,
	Srivatsa <vatsa@...ibm.com>, sekharan@...ibm.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	CKRM-Tech <ckrm-tech@...ts.sourceforge.net>,
	Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrey Savochkin <saw@...ru>,
	Matt Helsley <matthltc@...ibm.com>,
	Hugh Dickins <hugh@...itas.com>,
	Alexey Dobriyan <adobriyan@...l.ru>,
	Kirill Korotaev <dev@...ru>, Oleg Nesterov <oleg@...sign.ru>,
	devel@...nvz.org
Subject: Re: [ckrm-tech] [PATCH] BC: resource beancounters (v4) (added	user
 memory)

Balbir Singh wrote:
> Pavel Emelianov wrote:
>> Balbir Singh wrote:
>>> Dave Hansen wrote:
>>>> On Fri, 2006-09-08 at 11:33 +0400, Pavel Emelianov wrote:
>>>>> I'm afraid we have different understandings of what a "guarantee" is.
>>>> It appears so.
>>>>
>>>>> Don't we?
>>>>> Guarantee may be one of
>>>>>
>>>>>   1. container will be able to touch that number of pages
>>>>>   2. container will be able to sys_mmap() that number of pages
>>>>>   3. container will not be killed unless it touches that number of
>>>>> pages
>>>> A "death sentence" guarantee?  I like it. :)
>>>>
>>>>>   4. anything else
>>>>>
>>>>> Let's decide what kind of a guarantee we want.
>>> I think of guarantees w.r.t resources as the lower limit on the
>>> resource.
>>> Guarantees and limits can be thought of as the range (guarantee, limit]
>>> for the usage of the resource.
>>>
>>>> I think of it as: "I will be allowed to use this many total pages, and
>>>> they are guaranteed not to fail."  (1), I think.  The sum of all of
>>>> the
>>>> system's guarantees must be less than or equal to the amount of free
>>>> memory on the machine. 
>>> Yes, totally agree.
>>
>> Such a guarantee is really a limit and this limit is even harder than
>> BC's one :)
>>
>> E.g. I have a node with 1Gb of ram and 10 containers with 100Mb
>> guarantee each.
>> I want to start one more. What shall I do not to break guarantees?
>
> Don't start the new container or change the guarantees of the existing
> ones
> to accommodate this one :) The QoS design (done by the administrator)
> should
> take care of such use-cases. It would be perfectly ok to have a container
> that does not care about guarantees to set their guarantee to 0 and set
> their limit to the desired value. As Chandra has been stating we need two
> parameters (guarantee, limit), either can be optional, but not both.
If I set up 9 groups to have 100Mb limit then I have 100Mb assured (on
1Gb node)
for the 10th one exactly. And I do not have to set up any guarantee as
it won't affect
anything. So what a guarantee parameter is needed for?
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