Re: [PATCH net-next 2/3] vhost_net: support in order feature

[Jason Wang]

On 2018/11/23 äå11:49, Michael S. Tsirkin wrote:
> On Fri, Nov 23, 2018 at 11:00:15AM +0800, Jason Wang wrote:
> > This makes vhost_net to support in order feature. This is as simple as
> > use datacopy path when it was negotiated. An alternative is not to
> > advertise in order when zerocopy is enabled which tends to be
> > suboptimal consider zerocopy may suffer from e.g HOL issues.
> Well IIRC vhost_zerocopy_signal_used is used to
> actually reorder used ring to match available ring.
> So with a big comment explaining why it is so,
> we could just enable IN_ORDER there too.

The problem is we allow switching between zerocopy and datacopy.

And what's more important, if we allow in order for zerocopy, a single 
packet delay may hang all the rest.

Thanks