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SubjectRe: [RFC PATCH 00/17] virtual-bus
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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