[dpdk-dev] [PATCH 00/14] implement packed virtqueues

Jens Freimann jfreimann at redhat.com
Mon Jan 29 15:11:29 CET 2018

This is a basic implementation of packed virtqueues as specified in the
Virtio 1.1 draft. A compiled version of the current draft is available
at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at

It does not implement yet indirect descriptors and checksum offloading.
VIRTIO_F_IN_ORER is not implemented, as well as support for mergeable buffers
with packed queues. Patches for this will follow soon.  

A packed virtqueue is different from a split virtqueue in that it
consists of only a single descriptor ring that replaces available and
used ring, index and descriptor buffer. 

Each descriptor is readable and writable and has a flags field. These flags
will mark if a descriptor is available or used.  To detect new available descriptors
even after the ring has wrapped, device and driver each have a
single-bit wrap counter that is flipped from 0 to 1 and vice versa every time
the last descriptor in the ring is used/made available. 

The idea behind this is to 1. improve performance by avoiding cache misses
and 2. be easier for devices to implement.

Regarding performance: with these patches I get 21.13 Mpps on my system
as compared to 18.8 Mpps with the virtio 1.0 code. Packet size was 64
bytes, 0.05% acceptable loss.  Test setup is described as in

Packet generator:
Intel(R) Xeon(R) CPU E5-2665 0 @ 2.40GHz
Intel X710 NIC
RHEL 7.4

Device under test:
Intel(R) Xeon(R) CPU E5-2667 v4 @ 3.20GHz
Intel X710 NIC
RHEL 7.4

VM on DuT: RHEL7.4

I plan to do more performance test with bigger frame sizes.  

This patch series is based on a prototype implemented by Yuanhan Liu and
Tiwei Bie. 


Jens Freimann (10):
  net/virtio: vring init for packed queues
  net/virtio: don't call virtio_disable_intr() for packed queues
  net/virtio: add virtio 1.1 defines
  net/virtio: add packed virtqueue helpers
  net/virtio: don't dump split virtqueue data
  net/virtio: implement transmit path for packed queues
  vhost: add virtio 1.1 defines
  vhost: add helpers for packed virtqueues
  vhost: dequeue for packed queues
  vhost: packed queue enqueue path

Yuanhan Liu (4):
  net/virtio-user: add option to use packed queues
  net/virtio: implement receive path for packed queues
  vhost: vring address setup for packed queues
  vhost: enable packed virtqueues

 drivers/net/virtio/Makefile                      |   1 +
 drivers/net/virtio/virtio_ethdev.c               |  50 ++--
 drivers/net/virtio/virtio_ethdev.h               |   5 +
 drivers/net/virtio/virtio_pci.h                  |   8 +
 drivers/net/virtio/virtio_ring.h                 |  63 ++++-
 drivers/net/virtio/virtio_rxtx.c                 | 141 +++++++++-
 drivers/net/virtio/virtio_rxtx_1.1.c             | 161 ++++++++++++
 drivers/net/virtio/virtio_user/virtio_user_dev.c |  12 +-
 drivers/net/virtio/virtio_user/virtio_user_dev.h |   3 +-
 drivers/net/virtio/virtio_user_ethdev.c          |  15 +-
 drivers/net/virtio/virtqueue.c                   |   3 +
 drivers/net/virtio/virtqueue.h                   |  14 +-
 lib/librte_vhost/vhost.c                         |   5 +
 lib/librte_vhost/vhost.h                         |   7 +-
 lib/librte_vhost/vhost_user.c                    |  17 +-
 lib/librte_vhost/virtio-1.1.h                    |  63 +++++
 lib/librte_vhost/virtio_net.c                    | 321 ++++++++++++++++++++++-
 17 files changed, 859 insertions(+), 30 deletions(-)
 create mode 100644 drivers/net/virtio/virtio_rxtx_1.1.c
 create mode 100644 lib/librte_vhost/virtio-1.1.h


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