[dpdk-dev] [PATCH 0/5 for 2.3] vhost rxtx refactor

[Yuanhan Liu]

Vhost rxtx code is derived from vhost-switch example, which is very
likely the most messy code in DPDK. Unluckily, the move also brings
over the bad merits: twisted logic, bad comments.

When I joined this team firstly, I was quite scared off by the messy
and long vhost rxtx code. While adding the vhost-user live migration
support, that I have to make fews changes to it, I then ventured to
look at it again, to understand it better, in the meantime, to see if
I can refactor it.

And, here you go.

The first 3 patches refactor 3 major functions at vhost_rxtx.c,
respectively. It simplifies the code logic, making it more readable.
On the other hand, it reduces code size, due to a lot of same
code are removed.

Patch 4 gets rid of the rte_memcpy for virtio_hdr copy, which nearly
saves 12K bytes of code size!

Till now, the code has been greatly reduced: 39348 vs 24179.

Patch 5 removes "unlikely" for VIRTIO_NET_F_MRG_RXBUF detection.

Note that the code could be further simplified or reduced. However,
judging that it's a first try and it's the *key* data path, I guess
it's okay to not be radical and stop here so far.

Another note is that we should add more secure checks at rxtx side.
It could be a standalone task for v2.3, and this series is more
about refactor, hence I leave it for future enhancement.

---
Yuanhan Liu (5):
  vhost: refactor rte_vhost_dequeue_burst
  vhost: refactor virtio_dev_rx
  vhost: refactor virtio_dev_merge_rx
  vhost: do not use rte_memcpy for virtio_hdr copy
  vhost: don't use unlikely for VIRTIO_NET_F_MRG_RXBUF detection

 lib/librte_vhost/vhost_rxtx.c | 959 ++++++++++++++++++------------------------
 1 file changed, 407 insertions(+), 552 deletions(-)

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1.9.0