Re: [dpdk-dev] [PATCH v5 5/8] doc/ring: add zero copy peek APIs

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> 
> Add zero copy peek API documentation.
> 
> Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> ---
>  doc/guides/prog_guide/ring_lib.rst     | 41 ++++++++++++++++++++++++++
>  doc/guides/rel_notes/release_20_11.rst |  9 ++++++
>  2 files changed, 50 insertions(+)
> 
> diff --git a/doc/guides/prog_guide/ring_lib.rst b/doc/guides/prog_guide/ring_lib.rst
> index 895484d95..247646d38 100644
> --- a/doc/guides/prog_guide/ring_lib.rst
> +++ b/doc/guides/prog_guide/ring_lib.rst
> @@ -452,6 +452,47 @@ selected. As an example of usage:
>  Note that between ``_start_`` and ``_finish_`` none other thread can proceed
>  with enqueue(/dequeue) operation till ``_finish_`` completes.
> 
> +Ring Peek Zero Copy API
> +-----------------------
> +
> +Along with the advantages of the peek APIs, zero copy APIs provide the ability
> +to copy the data to the ring memory directly without the need for temporary
> +storage (for ex: array of mbufs on the stack).
> +
> +These APIs make it possible to split public enqueue/dequeue API into 3 phases:
> +
> +* enqueue/dequeue start
> +
> +* copy data to/from the ring
> +
> +* enqueue/dequeue finish
> +
> +Note that this API is available only for two sync modes:
> +
> +*   Single Producer/Single Consumer (SP/SC)
> +
> +*   Multi-producer/Multi-consumer with Head/Tail Sync (HTS)
> +
> +It is a user responsibility to create/init ring with appropriate sync modes.
> +Following is an example of usage:
> +
> +.. code-block:: c
> +
> +    /* Reserve space on the ring */
> +    n = rte_ring_enqueue_zc_burst_start(r, 32, &zcd, NULL);
> +    /* Pkt I/O core polls packets from the NIC */
> +    if (n != 0) {
> +        nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr1, zcd->n1);
> +        if (nb_rx == zcd->n1 && n != zcd->n1)
> +            nb_rx = rte_eth_rx_burst(portid, queueid, zcd->ptr2,
> +							n - zcd->n1);
> +        /* Provide packets to the packet processing cores */
> +        rte_ring_enqueue_zc_finish(r, nb_rx);
> +    }
> +
> +Note that between ``_start_`` and ``_finish_`` no other thread can proceed
> +with enqueue(/dequeue) operation till ``_finish_`` completes.
> +
>  References
>  ----------
> 
> diff --git a/doc/guides/rel_notes/release_20_11.rst b/doc/guides/rel_notes/release_20_11.rst
> index d8ac359e5..fdc78b3da 100644
> --- a/doc/guides/rel_notes/release_20_11.rst
> +++ b/doc/guides/rel_notes/release_20_11.rst
> @@ -55,6 +55,15 @@ New Features
>       Also, make sure to start the actual text at the margin.
>       =======================================================
> 
> +* **Added zero copy APIs for rte_ring.**
> +
> +  For rings with producer/consumer in ``RTE_RING_SYNC_ST``, ``RTE_RING_SYNC_MT_HTS``
> +  modes, these APIs split enqueue/dequeue operation into three phases
> +  (enqueue/dequeue start, copy data to/from ring, enqueue/dequeue finish).
> +  Along with the advantages of the peek APIs, these provide the ability to
> +  copy the data to the ring memory directly without the need for temporary
> +  storage.
> +
>  * **Added write combining store APIs.**
> 
>    Added ``rte_write32_wc`` and ``rte_write32_wc_relaxed`` APIs
> --

Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>

> 2.17.1