On Mon, Aug 13, 2012 at 02:41:47PM +0300, Gleb Natapov wrote: > On Mon, Aug 13, 2012 at 02:30:49PM +0300, Avi Kivity wrote: > > On 08/13/2012 02:12 PM, Gleb Natapov wrote: > > > On Mon, Aug 13, 2012 at 02:03:51PM +0300, Avi Kivity wrote: > > >> On 08/13/2012 02:01 PM, Gleb Natapov wrote: > > >> >> > > >> >> Actually this is overkill. Suppose we do an apicid->vcpu translation > > >> >> cache? Then we retain O(1) behaviour, no need for a huge cache. > > >> >> > > >> > Not sure I follow. > > >> > > >> Unicast MSIs and IPIs can be speeded up by looking up the vcpu using the > > >> apic id, using a static lookup table (only changed when the guest > > >> updates apicid or a vcpu is inserted). > > >> > > > To check that MSI/IPI is unicast you need to check a lot of things: delivery > > > mode, shorthand, dest mode, vector. In short everything but level. This > > > is exactly what kvm_irq_delivery_to_apic() is doing. Caching apicid->vcpu > > > is not enough, caching (delivery mode, shorthand, dest mode, > > > vector)->vcpu is enough and this is exactly what the patch does for irq > > > routing entries. > > > > > > apicid is checked in a loop, the others aren't. > Along with dest_id. > > > apicid is > > unpredicatable; the others are. > What do you mean "unpredicatable"? > > > > > I think we should use apicid loopup exclusively. It doesn't accelerate > > everything, but most things, and is common to all unicast interrupts > > except PIC (and we can also precompute the target vcpu for PIC, too). > > > We can change kvm_irq_delivery_to_apic() to avoid the loop if interrupt > is physical, logical is also not too hard. need two extra tables for cluster/non cluster. > non broadcast, non low prio. Do whatever it does now > otherwise. You think we do not need cache in such case? > > -- > Gleb. -- 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
