[dpdk-dev] [PATCH v12 00/10] implement packed virtqueues

Jens Freimann jfreimann at redhat.com
Thu Dec 13 13:34:43 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
https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf

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 pointers.

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.

With this patch set I see performance equal or slightly better (+2-3%) in a PVP
scenario compared to split virtqueues (v18.11 in host) 

regards,
Jens 


v11->v12:
 * add a patch to disable control vq when packed vq is enabled.
   I have a patch to support this but it needs a bit more work
   and I think it shouldn't stop this series from being applied
 * rework mergeable receive buffer code to be more efficient, by
   batching descriptor refill, similar to what Maxime proposed for
   split virtqueues
 * removed unnecessary checks in virtio_recv_mergeable_pkts_packed
   (Maxime) 
 * Did not merge receive functions as Maxime suggested because it seemed
   to cause a small performance regression
 * Move event_flags_shadow from patch 3 to 1 (Maxime)
 * Did not merge xmit functions and call _split/_packed functions from
   there because it seemed to cause small performance drop (-0.5%)
   (Maxime)

v10-v11:
 * this version includes some fixes from Tiwei, so I added his
   Signed-off-by to some of the patches
 * fix hang with mergable rx buffers (Tiwei)
 * clean-up code and simplify buffer handling (Tiwei)
 * rebase to current virtio-next master branch

v9-v10:
 * don't mix index into buffer list and descriptors
 * whitespace and formatting issues
 * remove "VQ:" in dump virtqueue patch
 * add extra packed vring struct to virtqueue and change function
   prototypes and code accordingly
 * move wrap_counters to virtqueue
 * make if-conditions for packed and !packed more clear in
   set_rxtx_funcs()
 * initialize wrap counters in first patch, instead of rx and tx
   implementation patch
 * make virtio-user not supported with packed virtqueues, to
   be fixed in other patch set?

v8-v9:
 * fix virtio_ring_free_chain_packed() to handle descriptors
   correctly in case of out-of-order
 * fix check in virtqueue_xmit_cleanup_packed() to improve performance

v7->v8:
 * move desc_is_used change to correct patch
 * remove trailing newline
 * correct xmit code, flags update and memory barrier
 * move packed desc init to dedicated function, split
   and packed variant


Jens Freimann (9):
  net/virtio: vring init for packed queues
  net/virtio: add packed virtqueue defines
  net/virtio: add packed virtqueue helpers
  net/virtio: dump packed virtqueue data
  net/virtio: implement transmit path for packed queues
  net/virtio: implement receive path for packed queues
  net/virtio: add virtio send command packed queue support
  net/virtio-user: ctrl virtqueue not supported with packed vqs
  net/virtio: enable packed virtqueues by default

Yuanhan Liu (1):
  net/virtio-user: add option to use packed queues

 drivers/net/virtio/virtio_ethdev.c            | 227 +++++--
 drivers/net/virtio/virtio_ethdev.h            |   8 +
 drivers/net/virtio/virtio_pci.h               |   7 +
 drivers/net/virtio/virtio_ring.h              |  64 +-
 drivers/net/virtio/virtio_rxtx.c              | 620 +++++++++++++++++-
 .../net/virtio/virtio_user/virtio_user_dev.c  |  25 +-
 .../net/virtio/virtio_user/virtio_user_dev.h  |   2 +-
 drivers/net/virtio/virtio_user_ethdev.c       |  14 +-
 drivers/net/virtio/virtqueue.c                |  22 +
 drivers/net/virtio/virtqueue.h                | 122 +++-
 10 files changed, 1035 insertions(+), 76 deletions(-)

-- 
2.17.2



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