Messages in this thread | | | Date | Fri, 03 Apr 2009 14:03:45 +0300 | From | Avi Kivity <> | Subject | Re: [RFC PATCH 00/17] virtual-bus |
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Gerd Hoffmann wrote: > Avi Kivity wrote: > >> There is no choice. Exiting from the guest to the kernel to userspace >> is prohibitively expensive, you can't do that on every packet. >> > > I didn't look at virtio-net very closely yet. I wonder why the > notification is that a big issue though. It is easy to keep the number > of notifications low without increasing latency: > > Check shared ring status when stuffing a request. If there are requests > not (yet) consumed by the other end there is no need to send a > notification. That scheme can even span multiple rings (nics with rx > and tx for example). >
If the host is able to consume a request immediately, and the guest is not able to batch requests, this breaks down. And that is the current situation.
-- I have a truly marvellous patch that fixes the bug which this signature is too narrow to contain.
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