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SubjectRe: [PATCH v3 3/6] vbus: add a "vbus-proxy" bus model for vbus_driver objects
Ingo Molnar wrote:
>> I think the reason vbus gets better performance for networking
>> today is that vbus' backends are in the kernel while virtio's
>> backends are currently in userspace. Since Michael has a
>> functioning in-kernel backend for virtio-net now, I suspect we're
>> weeks (maybe days) away from performance results. My expectation
>> is that vhost + virtio-net will be as good as venet + vbus. If
>> that's the case, then I don't see any reason to adopt vbus unless
>> Greg things there are other compelling features over virtio.
>>
>
> Keeping virtio's backend in user-space was rather stupid IMHO.
>

I don't think it's quite so clear.

There's nothing about vhost_net that would prevent a userspace
application from using it as a higher performance replacement for tun/tap.

The fact that we can avoid userspace for most of the fast paths is nice
but that's really an issue of vhost_net vs. tun/tap.

From the kernel's perspective, a KVM guest is just a userspace
process. Having new userspace interfaces that are only useful to KVM
guests would be a bad thing.

Regards,

Anthony Liguori


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