[dpdk-dev] [PATCH v2] vhost: Add indirect descriptors support to the TX path

[Stephen Hemminger]

On Fri, 23 Sep 2016 09:16:49 +0200
Maxime Coquelin <maxime.coquelin at redhat.com> wrote:

> Indirect descriptors are usually supported by virtio-net devices,
> allowing to dispatch a larger number of requests.
> 
> When the virtio device sends a packet using indirect descriptors,
> only one slot is used in the ring, even for large packets.
> 
> The main effect is to improve the 0% packet loss benchmark.
> A PVP benchmark using Moongen (64 bytes) on the TE, and testpmd
> (fwd io for host, macswap for VM) on DUT shows a +50% gain for
> zero loss.
> 
> On the downside, micro-benchmark using testpmd txonly in VM and
> rxonly on host shows a loss between 1 and 4%.i But depending on
> the needs, feature can be disabled at VM boot time by passing
> indirect_desc=off argument to vhost-user device in Qemu.
> 
> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>

What about supporting VIRTIO_F_ANY_LAYOUT?