[dpdk-dev] [PATCH v4 00/20] implement packed virtqueues

Jens Freimann jfreimann at redhat.com
Thu Apr 19 09:07:31 CEST 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
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf

It does not implement yet indirect descriptors and checksum offloading.

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
http://dpdk.org/doc/guides/howto/pvp_reference_benchmark.html

Packet generator:
MoonGen
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.



changes from v3->v4:
* added helpers to increment index and set available/used flags
* driver keeps track of number of descriptors used 
* change logic in set_rxtx_funcs()
* add patch for ctrl virtqueue with support for packed virtqueues
* rename virtio-1.1.h to virtio-packed.h
* fix wrong sizeof() in "vhost: vring address setup for packed queues"
* fix coding style of function definition in "net/virtio: add packed
  virtqueue helpers"
* fix padding in vring_size()
* move patches to enable packed virtqueues end of series
* v4 has two open problems: I'm sending it out anyway for feedback/help:
 * when VIRTIO_NET_F_MRG_RXBUF enabled only 128 packets are send in
   guest, i.e. when ring is full for the first time. I suspect a bug in
   setting the avail/used flags

changes from v2->v3:
* implement event suppression
* add code do dump packed virtqueues
* don't use assert in vhost code
* rename virtio-user parameter to packed-vq
* support rxvf flush 

changes from v1->v2:
* don't use VIRTQ_DESC_F_NEXT in used descriptors (Jason)
* no rte_panice() in guest triggerable code (Maxime)
* use unlikely when checking for vq (Maxime)
* rename everything from _1_1 to _packed  (Yuanhan)
* add two more patches to implement mergeable receive buffers 


Jens Freimann (16):
  net/virtio: vring init for packed queues
  net/virtio: add virtio 1.1 defines
  net/virtio: add packed virtqueue helpers
  net/virtio: flush packed receive virtqueues
  net/virtio: dump packed virtqueue data
  net/virtio: implement transmit path for packed queues
  net/virtio: add virtio send command packed queue support
  net/virtio: add support for mergeable buffers with packed virtqueues
  net/virtio: add support for event suppression
  vhost: add virtio packed virtqueue defines
  vhost: add helpers for packed virtqueues
  vhost: dequeue for packed queues
  vhost: packed queue enqueue path
  vhost: add support for mergeable buffers with packed virtqueues
  vhost: add event suppression for packed queues
  net/virtio: by default disable packed virtqueues

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: by default disable packed virtqueues

 config/common_base                               |   2 +
 drivers/net/virtio/virtio_ethdev.c               | 127 +++++-
 drivers/net/virtio/virtio_ethdev.h               |   5 +
 drivers/net/virtio/virtio_pci.h                  |   8 +
 drivers/net/virtio/virtio_ring.h                 |  97 ++++-
 drivers/net/virtio/virtio_rxtx.c                 | 357 +++++++++++++++-
 drivers/net/virtio/virtio_user/virtio_user_dev.c |   6 +-
 drivers/net/virtio/virtio_user/virtio_user_dev.h |   3 +-
 drivers/net/virtio/virtio_user_ethdev.c          |  15 +-
 drivers/net/virtio/virtqueue.c                   |  16 +
 drivers/net/virtio/virtqueue.h                   | 113 ++++-
 lib/librte_vhost/socket.c                        |   5 +
 lib/librte_vhost/vhost.c                         |  16 +
 lib/librte_vhost/vhost.h                         |  70 +++-
 lib/librte_vhost/vhost_user.c                    |  45 +-
 lib/librte_vhost/virtio-packed.h                 |  86 ++++
 lib/librte_vhost/virtio_net.c                    | 503 +++++++++++++++++++++--
 17 files changed, 1398 insertions(+), 76 deletions(-)
 create mode 100644 lib/librte_vhost/virtio-packed.h

-- 
2.14.3



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