On 12/21/2009 10:04 AM, Gregory Haskins wrote:
No, B and C definitely are, but A is lacking. And the performance suffers as a result in my testing (vhost-net still throws a ton of exits as its limited by virtio-pci and only adds about 1Gb/s to virtio-u, far behind venet even with things like zero-copy turned off).
How does virtio-pci limit vhost-net? The only time exits should occur are when the guest notifies the host that something has been placed on the ring. Since vhost-net has no tx mitigation scheme right now, the result may be that it's taking an io exit on every single packet but this is orthogonal to virtio-pci.
Since virtio-pci supports MSI-X, there should be no IO exits on host->guest notification other than EOI in the virtual APIC. This is a light weight exit today and will likely disappear entirely with newer hardware.
Regards, Anthony Liguori -- 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
