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

[Balbir Singh <balbir@in.ibm.com>]

Pavel Emelianov wrote:
> 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?

This use case works well for providing guarantee to one container. What if
I want guarantees of 100Mb and 200Mb for two containers? How do I setup
the system using limits?

Even I restrict everyone else to 700Mb. With this I cannot be sure that
the remaining 300Mb will be distributed as 100Mb and 200Mb.


--

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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