Virtualization - Aug 2012 - [Question]About KVM network zero-copy feature!

Hi,All

I searched from git-log, and found that until now we have vhost TX zero-copy
experiment feature, how
about RX zero-copy?

For XEN, net-back also only has TX zero-copy, Is there any reason that RX
zero-copy still not implemented?

Thanks!

On Fri, 10 Aug 2012 11:34:32 +0800
"Peter Huang(Peng)" <peter.huangpeng at huawei.com> wrote:
> Hi,All
> 
> I searched from git-log, and found that until now we have vhost TX
zero-copy experiment feature, how
> about RX zero-copy?
> 
> For XEN, net-back also only has TX zero-copy, Is there any reason that RX
zero-copy still not implemented?
> 
There is no guarantee that packet will ever be read by receiver. This means
zero-copy could
create memory back pressure stalls.

Last patchset version was this:
[PATCH v16 00/17] Provide a zero-copy method on KVM virtio-net

IIRC the main issue was the need to integrate the patchset with
macvtap (as opposed to using a separate device).

On Mon, Aug 13, 2012 at 09:24:54AM +0800, Peter Huang(Peng)
wrote:
> Hi, Michael
> 
> IIt will be usefull if we can implement rx zero-copy, could you give
>  me some help if you know some technical details or some
> references on the internet?
> 
> I am wondering may be I can take a deep look on it first then decide
> if I can take it over or not.
> 
> Thanks a lot.
> 
> On 2012/8/12 17:37, Michael S. Tsirkin wrote:
> > On Sat, Aug 11, 2012 at 08:42:44PM -0400, Robert Vineyard wrote:
> >> (adding Xin Xiaohui to the conversation for comment)
> >>
> >> According to the NetworkingTodo page on the KVM wiki, zero-copy RX
> >> for macvtap is in fact on the roadmap, assigned to Xin:
> >>
> >> http://www.linux-kvm.org/page/NetworkingTodo
> > AFAIK Xin left Intel and is not working on it.
> > Contributions are welcome.
> >