On 07/11/2012 10:57 PM, Alex Williamson wrote: >> >> > We still have classic KVM device assignment to provide fast-path INTx. >> > But if we want to replace it midterm, I think it's necessary for VFIO to >> > be able to provide such a path as well. >> >> I would like VFIO to have no regressions vs. kvm device assignment, >> except perhaps in uncommon corner cases. So I agree. > > I ran a few TCP_RR netperf tests forcing a 1Gb tg3 nic to use INTx. > Without irqchip support vfio gets a bit more than 60% of KVM device > assignment. That's a little bit of an unfair comparison since it's more > than just the I/O path. With the proposed interfaces here, enabling > irqchip, vfio is within 10% of KVM device assignment for INTx. For MSI, > I can actually make vfio come out more than 30% better than KVM device > assignment if I send the eventfd from the hard irq handler. Using a > threaded handler as the code currently does, vfio is still behind KVM. > It's hard to beat a direct call chain. We can have a direct call chain with vfio too, using a custom eventfd poll function, no? Assuming we set up a fast path for unicast msi. > For more devices, one that seems common among the non-enterprise users > are TV capture cards, like the old PVR-250/350 devices. These don't > support MSI. Thanks, That doesn't mean they require an interrupt rate that warrants a fast path. But I guess that some combination of old guests or old hardware will want it. -- error compiling committee.c: too many arguments to function -- 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
