[dpdk-dev] [RFC] vhost: Add indirect descriptors support to the TX path

[Yuanhan Liu]

On Fri, Aug 05, 2016 at 02:18:42PM +0200, Maxime Coquelin wrote:
> 
> 
> On 08/03/2016 04:03 PM, Yuanhan Liu wrote:
> >On Tue, Jul 12, 2016 at 04:32:12PM +0200, Maxime Coquelin wrote:
> >>Indirect descriptors are usually supported by virtio-net devices,
> >>allowing to dispatch a large number of large requests.
> >>
> >>When the virtio device sends a packet using indirect descriptors,
> >>only one slot is used in the ring, even for large packets.
> >>
> >>Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
> >>---
> >>I have a two questions regarding the implementation of this feature:
> >>
> >>1. Should I add a check to ensure the indirect feature is supported
> >>(i.e. the negociation succeeded) when having an indirect desc?
> >>
> >>2. Should I check in copy_desc_to_mbuf() that we don't have a nested
> >>indirect descriptor?
> >>
> >>Both these sanity checks are recommended from the virtio spec, but
> >>since it is to be done in the hot path, it may introduce some
> >>performance penalties.
> >>
> >>Note that the first check is not done in the Kernel vhost driver, whereas
> >>the second one is.
> >
> >I think we could firstly follow the Linux kernel implementation.
> OK, I can do that in the v2.

FYI, I'm waiting for it.

	--yliu