[dpdk-dev] [PATCH v2 0/9] ethdev: introduce Rx buffer split

[Viacheslav Ovsiienko]

The DPDK datapath in the transmit direction is very flexible.
An application can build the multi-segment packet and manages
almost all data aspects - the memory pools where segments
are allocated from, the segment lengths, the memory attributes
like external buffers, registered for DMA, etc.

In the receiving direction, the datapath is much less flexible,
an application can only specify the memory pool to configure the
receiving queue and nothing more. In order to extend receiving
datapath capabilities it is proposed to add the way to provide
extended information how to split the packets being received.

The following structure is introduced to specify the Rx packet
segment:

struct rte_eth_rxseg {
    struct rte_mempool *mp; /* memory pools to allocate segment from */
    uint16_t length; /* segment maximal data length */
    uint16_t offset; /* data offset from beginning of mbuf data buffer */
    uint32_t reserved; /* reserved field */
};

The new routine rte_eth_rx_queue_setup_ex() is introduced to
setup the given Rx queue using the new extended Rx packet segment
description:

int
rte_eth_rx_queue_setup_ex(uint16_t port_id, uint16_t rx_queue_id,
                          uint16_t nb_rx_desc, unsigned int socket_id,
                          const struct rte_eth_rxconf *rx_conf,
                          const struct rte_eth_rxseg *rx_seg,
                          uint16_t n_seg)

This routine presents the two new parameters:
    rx_seg - pointer the array of segment descriptions, each element
             describes the memory pool, maximal data length, initial
             data offset from the beginning of data buffer in mbuf
    n_seg - number of elements in the array

The new offload flag DEV_RX_OFFLOAD_BUFFER_SPLIT in device
capabilities is introduced to present the way for PMD to report to
application about supporting Rx packet split to configurable
segments. Prior invoking the rte_eth_rx_queue_setup_ex() routine
application should check DEV_RX_OFFLOAD_BUFFER_SPLIT flag.

If the Rx queue is configured with new routine the packets being
received will be split into multiple segments pushed to the mbufs
with specified attributes. The PMD will allocate the first mbuf
from the pool specified in the first segment descriptor and puts
the data staring at specified offset in the allocated mbuf data
buffer. If packet length exceeds the specified segment length
the next mbuf will be allocated according to the next segment
descriptor (if any) and data will be put in its data buffer at
specified offset and not exceeding specified length. If there is
no next descriptor the next mbuf will be allocated and filled in the
same way (from the same pool and with the same buffer offset/length)
as the current one.

For example, let's suppose we configured the Rx queue with the
following segments:
    seg0 - pool0, len0=14B, off0=RTE_PKTMBUF_HEADROOM
    seg1 - pool1, len1=20B, off1=0B
    seg2 - pool2, len2=20B, off2=0B
    seg3 - pool3, len3=512B, off3=0B

The packet 46 bytes long will look like the following:
    seg0 - 14B long @ RTE_PKTMBUF_HEADROOM in mbuf from pool0
    seg1 - 20B long @ 0 in mbuf from pool1
    seg2 - 12B long @ 0 in mbuf from pool2

The packet 1500 bytes long will look like the following:
    seg0 - 14B @ RTE_PKTMBUF_HEADROOM in mbuf from pool0
    seg1 - 20B @ 0 in mbuf from pool1
    seg2 - 20B @ 0 in mbuf from pool2
    seg3 - 512B @ 0 in mbuf from pool3
    seg4 - 512B @ 0 in mbuf from pool3
    seg5 - 422B @ 0 in mbuf from pool3

The offload DEV_RX_OFFLOAD_SCATTER must be present and
configured to support new buffer split feature (if n_seg
is greater than one).

The new approach would allow splitting the ingress packets into
multiple parts pushed to the memory with different attributes.
For example, the packet headers can be pushed to the embedded
data buffers within mbufs and the application data into
the external buffers attached to mbufs allocated from the
different memory pools. The memory attributes for the split
parts may differ either - for example the application data
may be pushed into the external memory located on the dedicated
physical device, say GPU or NVMe. This would improve the DPDK
receiving datapath flexibility with preserving compatibility
with existing API.

Also, the proposed segment description might be used to specify
Rx packet split for some other features. For example, provide
the way to specify the extra memory pool for the Header Split
feature of some Intel PMD.

Signed-off-by: Viacheslav Ovsiienko <viacheslavo at nvidia.com>

---
[RFC]: http://patches.dpdk.org/patch/75582/
Related deprecation note (revoked): http://patches.dpdk.org/patch/75205/

v1: http://patches.dpdk.org/patch/79594/
v2: add feature supoport to mlx5 PMD

Viacheslav Ovsiienko (9):
  ethdev: introduce Rx buffer split
  app/testpmd: add multiple pools per core creation
  app/testpmd: add buffer split offload configuration
  app/testpmd: add rxpkts commands and parameters
  app/testpmd: add extended Rx queue setup
  net/mlx5: add extended Rx queue setup routine
  net/mlx5: configure Rx queue to support split
  net/mlx5: register multiple pool for Rx queue
  net/mlx5: update Rx datapath to support split

 app/test-pmd/bpf_cmd.c                      |   4 +-
 app/test-pmd/cmdline.c                      |  96 +++++++++++---
 app/test-pmd/config.c                       |  63 ++++++++-
 app/test-pmd/parameters.c                   |  39 +++++-
 app/test-pmd/testpmd.c                      | 108 +++++++++++-----
 app/test-pmd/testpmd.h                      |  41 +++++-
 doc/guides/nics/features.rst                |  15 +++
 doc/guides/rel_notes/release_20_11.rst      |   6 +
 doc/guides/testpmd_app_ug/run_app.rst       |  16 ++-
 doc/guides/testpmd_app_ug/testpmd_funcs.rst |  21 ++-
 drivers/net/mlx5/linux/mlx5_os.c            |   2 +
 drivers/net/mlx5/mlx5.h                     |   3 +
 drivers/net/mlx5/mlx5_mr.c                  |   3 +
 drivers/net/mlx5/mlx5_rxq.c                 | 194 +++++++++++++++++++++++-----
 drivers/net/mlx5/mlx5_rxtx.c                |   3 +-
 drivers/net/mlx5/mlx5_rxtx.h                |  10 +-
 drivers/net/mlx5/mlx5_trigger.c             |  20 +--
 lib/librte_ethdev/rte_ethdev.c              | 174 +++++++++++++++++++++++++
 lib/librte_ethdev/rte_ethdev.h              |  16 +++
 lib/librte_ethdev/rte_ethdev_driver.h       |  10 ++
 20 files changed, 733 insertions(+), 111 deletions(-)

-- 
1.8.3.1