Messages in this thread | | | Date | Thu, 1 Oct 2009 00:30:39 +0200 | From | Herbert Poetzl <> | Subject | Re: [RFC v2 PATCH 0/8] CFS Hard limits - v2 |
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On Wed, Sep 30, 2009 at 09:00:53PM +0530, Balbir Singh wrote: > * Pavel Emelyanov <xemul@openvz.org> [2009-09-30 19:10:27]: > > Balbir Singh wrote: > > > * Pavel Emelyanov <xemul@openvz.org> [2009-09-30 17:36:29]: > > >> Bharata B Rao wrote: > > >>> Hi, > > >>> > > >>> Here is the v2 post of hard limits feature for CFS group scheduler. This > > >>> RFC post mainly adds runtime borrowing feature and has a new locking scheme > > >>> to protect CFS runtime related fields. > > >>> > > >>> It would be nice to have some comments on this set! > > >> I have a question I'd like to ask before diving into the code. > > >> Consider I'm a user, that has a 4CPUs box 2GHz each and I'd like > > >> to create a container with 2CPUs 1GHz each. Can I achieve this > > >> after your patches? > > > > > > I don't think the GHz makes any sense, consider CPUs with frequency > > > scaling. If I can scale from 1.6GHz to say 2.6GHz or 2GHz to 4GHz, > > > what does it mean for hard limit control? Hard limits define control > > > over existing bandwidth, anything else would be superficial and hard > > > hard to get right for both developers and users. > > > > Two numbers for configuring limits make even less sense OTOH ;) > > By assigning 2GHz for 4GHz CPU I obviously want half of its power ;) > > Please, see my reply to vatsa@ in this thread.
> But it makes life more difficult for the administrator to think in > terms of GHz -- no? Specifically with different heterogeneous systems. > I think it would be chaotic in a data center to configure GHz for > every partition. Not to say that it makes it even more confusing when > running on top of KVM. Lets say I create two vCPUs and I specifiy GHz > outside, do I expect to see it in /proc/cpuinfo?
> I'd like to hear what others think about GHz as well.
for me, using something like GHz or even BogoMips would not make any sense whatsoever ... I would be able to understand percentage, but this has some other implications as it does not handle granularity ....
Linux-VServer uses interval and rate, which is very similar to your setup, except that we use two pairs to achive a differentiation for 'busy' and 'idle' cases, i.e. when the cpu(s) would go idle, we switch from R1/I1 to R2/I2 for all guests, allowing to distribute the excess differently than the 'active' part ... but only one set is needed for hard limits ...
best, Herbert
> -- > Balbir
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