Messages in this thread | | | Subject | Re: [ckrm-tech] [Devel] Re: [PATCH] BC: resource beancounters (v4) (added user memory) | From | Chandra Seetharaman <> | Date | Mon, 18 Sep 2006 17:02:27 -0700 |
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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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