* Anthony Liguori (anthony@xxxxxxxxxxxxx) wrote: > On 12/02/2010 01:14 PM, Chris Wright wrote: > >* Anthony Liguori (aliguori@xxxxxxxxxx) wrote: > >>In certain use-cases, we want to allocate guests fixed time slices where idle > >>guest cycles leave the machine idling. There are many approaches to achieve > >>this but the most direct is to simply avoid trapping the HLT instruction which > >>lets the guest directly execute the instruction putting the processor to sleep. > >I like the idea, esp to keep from burning power. > > > >>Introduce this as a module-level option for kvm-vmx.ko since if you do this > >>for one guest, you probably want to do it for all. A similar option is possible > >>for AMD but I don't have easy access to AMD test hardware. > >Perhaps it should be a VM level option. And then invert the notion. > >Create one idle domain w/out hlt trap. Give that VM a vcpu per pcpu > >(pin in place probably). And have that VM do nothing other than hlt. > >Then it's always runnable according to scheduler, and can "consume" the > >extra work that CFS wants to give away. > > That's an interesting idea. I think Vatsa had some ideas about how > to do this with existing mechanisms. Yeah, should Just Work (TM) w/ smth like evilcap. > I'm interesting in comparing behavior with fixed allocation because > one thing the above relies upon is that the filler VM loses it's > time when one of the non-filler VCPU needs to run. Priorites? > This may all > work correctly but I think it's easier to rationalize about having > each non-filler VCPU have a fixed (long) time slice. If a VCPU > needs to wake up to become non-idle, it can do so immediately > because it already has the PCPU. The flipside...dont' have to worry about the issues that Marcelo brought up. Should be pretty easy to compare though. thanks, -chris -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
