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%. 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@redhat.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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