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

Michael S. Tsirkin mst at redhat.com
Fri Sep 23 20:31:27 CEST 2016


On Fri, Sep 23, 2016 at 11:24:16AM -0700, Stephen Hemminger wrote:
> 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?

I thought it's already supported.
That's required by virtio 1 and dpdk claims support for that.

-- 
MST


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