Messages in this thread | | | Date | Mon, 21 Dec 2009 10:37:03 -0600 | From | Anthony Liguori <> | Subject | Re: [GIT PULL] AlacrityVM guest drivers for 2.6.33 |
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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
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