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    SubjectRe: [ckrm-tech] [Devel] Re: [PATCH] BC: resource beancounters (v4) (added user memory)
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    On Sat, 2006-09-16 at 01:21 +0400, Kir Kolyshkin wrote:
    > Rohit Seth wrote:
    > > On Fri, 2006-09-15 at 13:26 +0400, Kirill Korotaev wrote:
    > >
    > > <...skipped...>
    > >
    > >> for VMware which can reserve required amount of RAM for VM.
    > >>
    > >
    > > It is much easier to provide guarantees in complete virtual
    > > environments. But then you pay the cost in terms of performance.
    > >
    > "Complete virtual environments" vs. "contaners" is not [only] about
    > performance! In the end, given a proper set of dirty and no-so-dirty
    > hacks in software and hardware, their performance will be close to native.
    >
    > Containers vs. other virtualization types is more about utilization,
    > density, scalability, portability.
    >
    > Speaking of guarantees, yes, guarantees is easy, you just reserve such
    > amount of RAM for your VM and that is all. But the fact is usually some
    > part of that RAM will not be utilized by this particular VM. But since
    > it is reserved, it can not be utilized by other VMs -- and we end up
    > just wasting some resources. Containers, given a proper resource
    > management and configuration, can have some guarantees and still be able
    > to utilize all the RAM available in the system. This difference can be
    > metaphorically expressed as a house divided into rooms. Dividing walls
    > can either be hard or flexible. With flexible walls, room (container)
    > owner have a guarantee of minimal space in your room, but if a few
    > guests come for a moment, the walls can move to make more space (up to
    > the limit). So the flexibility is measured as the delta between a
    > guarantee and a limit.
    >
    > This flexibility leads to higher utilization, and this flexibility is
    > one of the reasons for better density (a few times higher than that of a
    > paravirtualization solution).
    >
    > I will not touch scalability and portability topics here to make things
    > simpler.
    > > I think we should punt on hard guarantees and fractions for the first
    > > draft. Keep the implementation simple.
    > >
    > Do I understand it right that with hard guarantees we loose the
    > flexibility I have just described? If this is the case, I do not like it.
    >

    If I understand your description correctly (describing flexibility to be
    the ability to move the resource usage between guarantee and limit),
    then NO, you will not loose that flexibility.

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    --

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


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