>> A VF interrupt usually happens in 4-8KHZ. How about the virtio? >> I assume virtio will be widely used together w/ leagcy guest with >> INTx mode. >> > > True, but in time it will be replaced by MSI. > > Note without vhost virtio is also in userspace, so there are lots of > exits anyway for the status register. Few months ago, we noticed the interrupt frequency of PV I/O in previous solution is almost same with physical NIC interrupt which ticks in ~4KHZ. Each PV I/O frontend driver (or its interrupt source) has similar interrupt frequency which means Nx more interrupt. I guess virtio is in similar situation. We then did an optimization for PV IO to mitigate the interrupt to guest by setting interrupt throttle in backend side, because native NIC also does in that way -- so called ITR register in Intel NIC. We can see 30-90% CPU utilization saving depending on how many frontend driver interrupt is employed. Not sure if it is adopted in vhost side. One drawback of course is the latency, but it is mostly tolerable if it is reduced to ~1KHZ. Thx, Eddie-- 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
