[RFC,v2 0/2] vhost: support async dequeue data path

[xuan.ding@intel.com]

From: Xuan Ding <xuan.ding@intel.com>

The presence of an asynchronous path allows applications to offload
memory copies to DMA engine, so as to save CPU cycles and improve
the copy performance. This patch set is a draft implementation for
split ring in vhost async dequeue data path. The code is based on
latest enqueue changes [1].

This patch set is a new design and implementation of [2]. Since dmadev
was introduced in DPDK 21.11, to simplify application logics, this patch
integrates dmadev in vhost. With dmadev integrated, vhost supports M:N
mapping between vrings and DMA virtual channels. Specifically, one vring
can use multiple different DMA channels and one DMA channel can be
shared by multiple vrings at the same time.

A new asynchronous dequeue function is introduced:
	1) rte_vhost_async_try_dequeue_burst(int vid, uint16_t queue_id,
       		struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts,
		uint16_t count, int *nr_inflight,
		uint16_t dma_id, uint16_t vchan_id)

	Receive packets from the guest and offloads copies to DMA
virtual channel.

[1] https://mails.dpdk.org/archives/dev/2022-February/234555.html
[2] https://mails.dpdk.org/archives/dev/2021-September/218591.html

RFC v1 -> v2:
* fix one bug in example
* rename vchan to vchan_id
* check if dma_id and vchan_id valid
* rework all the logs to new standard

Xuan Ding (2):
  vhost: support async dequeue for split ring
  examples/vhost: support async dequeue data path

 doc/guides/sample_app_ug/vhost.rst |   9 +-
 examples/vhost/main.c              | 292 +++++++++++------
 examples/vhost/main.h              |  35 +-
 examples/vhost/virtio_net.c        |  16 +-
 lib/vhost/rte_vhost_async.h        |  33 ++
 lib/vhost/version.map              |   1 +
 lib/vhost/vhost.h                  |   1 +
 lib/vhost/virtio_net.c             | 504 +++++++++++++++++++++++++++++
 8 files changed, 793 insertions(+), 98 deletions(-)

-- 
2.17.1