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Re: [Qemu-devel] updated: kvm networking todo wiki
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] updated: kvm networking todo wiki |
Date: |
Thu, 30 May 2013 09:41:07 -0500 |
User-agent: |
Notmuch/0.15.2+77~g661dcf8 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
"Michael S. Tsirkin" <address@hidden> writes:
> On Thu, May 30, 2013 at 08:40:47AM -0500, Anthony Liguori wrote:
>> Stefan Hajnoczi <address@hidden> writes:
>>
>> > On Thu, May 30, 2013 at 7:23 AM, Rusty Russell <address@hidden> wrote:
>> >> Anthony Liguori <address@hidden> writes:
>> >>> Rusty Russell <address@hidden> writes:
>> >>>> On Fri, May 24, 2013 at 08:47:58AM -0500, Anthony Liguori wrote:
>> >>>>> FWIW, I think what's more interesting is using vhost-net as a
>> >>>>> networking
>> >>>>> backend with virtio-net in QEMU being what's guest facing.
>> >>>>>
>> >>>>> In theory, this gives you the best of both worlds: QEMU acts as a first
>> >>>>> line of defense against a malicious guest while still getting the
>> >>>>> performance advantages of vhost-net (zero-copy).
>> >>>>>
>> >>>> It would be an interesting idea if we didn't already have the vhost
>> >>>> model where we don't need the userspace bounce.
>> >>>
>> >>> The model is very interesting for QEMU because then we can use vhost as
>> >>> a backend for other types of network adapters (like vmxnet3 or even
>> >>> e1000).
>> >>>
>> >>> It also helps for things like fault tolerance where we need to be able
>> >>> to control packet flow within QEMU.
>> >>
>> >> (CC's reduced, context added, Dmitry Fleytman added for vmxnet3 thoughts).
>> >>
>> >> Then I'm really confused as to what this would look like. A zero copy
>> >> sendmsg? We should be able to implement that today.
>> >>
>> >> On the receive side, what can we do better than readv? If we need to
>> >> return to userspace to tell the guest that we've got a new packet, we
>> >> don't win on latency. We might reduce syscall overhead with a
>> >> multi-dimensional readv to read multiple packets at once?
>> >
>> > Sounds like recvmmsg(2).
>>
>> Could we map this to mergable rx buffers though?
>>
>> Regards,
>>
>> Anthony Liguori
>
> Yes because we don't have to complete buffers in order.
What I meant though was for GRO, we don't know how large the received
packet is going to be. Mergable rx buffers lets us allocate a pool of
data for all incoming packets instead of allocating max packet size *
max packets.
recvmmsg expects an array of msghdrs and I presume each needs to be
given a fixed size. So this seems incompatible with mergable rx
buffers.
Regards,
Anthony Liguori
>
>> >
>> > Stefan
- Re: [Qemu-devel] updated: kvm networking todo wiki, (continued)
- Re: [Qemu-devel] updated: kvm networking todo wiki, Anthony Liguori, 2013/05/24
- Re: [Qemu-devel] updated: kvm networking todo wiki, Michael S. Tsirkin, 2013/05/24
- Re: [Qemu-devel] updated: kvm networking todo wiki, Rusty Russell, 2013/05/29
- Re: [Qemu-devel] updated: kvm networking todo wiki, Anthony Liguori, 2013/05/29
- Re: [Qemu-devel] updated: kvm networking todo wiki, Michael S. Tsirkin, 2013/05/29
- Re: [Qemu-devel] updated: kvm networking todo wiki, Rusty Russell, 2013/05/30
- Re: [Qemu-devel] updated: kvm networking todo wiki, Stefan Hajnoczi, 2013/05/30
- Re: [Qemu-devel] updated: kvm networking todo wiki, Rusty Russell, 2013/05/30
- Re: [Qemu-devel] updated: kvm networking todo wiki, Anthony Liguori, 2013/05/30
- Re: [Qemu-devel] updated: kvm networking todo wiki, Michael S. Tsirkin, 2013/05/30
- Re: [Qemu-devel] updated: kvm networking todo wiki,
Anthony Liguori <=
- Re: [Qemu-devel] updated: kvm networking todo wiki, Anthony Liguori, 2013/05/30