On Thu, Apr 9, 2015 at 12:01 AM, Nikolay Nikolaev <n.nikol...@virtualopensystems.com> wrote: > On Thu, Apr 9, 2015 at 12:20 AM, Christoffer Dall > <christoffer.d...@linaro.org> wrote: >> Now when we have a host generic PCIe controller in the virt board, it >> would be nice to be able to use MSIs so that we can eventually enable >> VHOST with KVM. >> >> With these patches you can use MSIs with TCG and with KVM, but you still >> need some fixes for the mapping of the IRQ index to the GSI number for >> IRQFD to work. A separate patch series will follow this one to enable >> that. >> >> Tested with KVM on XGene and with TCG by configuring a virtio-pci >> network adapter for the guest and verifying MSIs going through as >> expected. > > Christofer, have you measured the network performance difference with KVM. > Probably the next patchseries (with IRQFD) makes bigger difference. > I did run numbers, and it depends greatly on the workload, but for something simple like netperf, you see a huge increase in performance (several orders of magnitude). Surprisingly, a large portion of that seems to come from using ioeventfd for the mmio accesses to vhost, possibly because it begins to use multiple queues. For latency measurements, irqfd also makes a big difference.
-Christoffer
