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

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Message-Id: <1158000262.6029.26.camel@linuxchandra>
Date:	Mon, 11 Sep 2006 11:44:22 -0700
From:	Chandra Seetharaman <sekharan@...ibm.com>
To:	Pavel Emelianov <xemul@...nvz.org>
Cc:	balbir@...ibm.com, Dave Hansen <haveblue@...ibm.com>,
	Rik van Riel <riel@...hat.com>, Srivatsa <vatsa@...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)

On Mon, 2006-09-11 at 10:56 +0400, Pavel Emelianov wrote:

<snip>

> >> 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.

In the first place system administrator should not be configuring it
that way, Then they are using it as a strict hard limit than guarantee
(as the resources guaranteed to one container is _not_ available to
others).

Besides, the above configuration is clearly _not_ work conservative.

They should use both guarantee and limit to associate resources to a
container/RG.

> I want to start one more. What shall I do not to break guarantees?

CKRM/RG handles it this way:

Amount of a resource a child RG gets is the ratio of its share value to
the parent's total # of shares. Children's resource allocation can be
changed just by changing the parent's total # of shares.

If you case about initial situation would be:
  Total memory in the system 100MB 
  parent's total # of shares: 100 (1 share == 1MB)
  10 children with # of shares: 10 (i.e each children has 10MB)

When I want to add another child, just change parent's total # of shares
to be say 125:
  Total memory in the system 100MB
  parent's total # of shares: 125 (1 share == 0.8MB)
  10 children with # of shares: 10 (i.e each children has 8MB)
Now you are left with 25 shares (or 20MB) that you can assign to new
child(ren) as you please.

<snip>
-- 

----------------------------------------------------------------------
    Chandra Seetharaman               | Be careful what you choose....
              - sekharan@...ibm.com   |      .......you may get it.
----------------------------------------------------------------------


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