> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of John McNamara
> Sent: Wednesday, February 25, 2015 7:46 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH 3/3] doc: add docs for the rxtx_callbacks sample
> app
>
> Added a sample application guide for the rxtx_callbacks app.
>
> Signed-off-by: John McNamara <john.mcnamara at intel.com>
> ---
> MAINTAINERS | 1 +
> doc/guides/sample_app_ug/index.rst | 1 +
> doc/guides/sample_app_ug/rxtx_callbacks.rst | 251
> +++++++++++++++++++++++++++
> 3 files changed, 253 insertions(+), 0 deletions(-) create mode 100644
> doc/guides/sample_app_ug/rxtx_callbacks.rst
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 86c1c6b..2ddb312 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -443,6 +443,7 @@ F: doc/guides/sample_app_ug/quota_watermark.rst
> M: Bruce Richardson <bruce.richardson at intel.com>
> M: John McNamara <john.mcnamara at intel.com>
> F: examples/rxtx_callbacks/
> +F: doc/guides/sample_app_ug/rxtx_callbacks.rst
>
> M: Bruce Richardson <bruce.richardson at intel.com>
> M: John McNamara <john.mcnamara at intel.com> diff --git
> a/doc/guides/sample_app_ug/index.rst
> b/doc/guides/sample_app_ug/index.rst
> index 4e9d59b..4a86459 100644
> --- a/doc/guides/sample_app_ug/index.rst
> +++ b/doc/guides/sample_app_ug/index.rst
> @@ -44,6 +44,7 @@ Sample Applications User Guide
> exception_path
> hello_world
> skeleton
> + rxtx_callbacks
> ip_frag
> ipv4_multicast
> ip_reassembly
> diff --git a/doc/guides/sample_app_ug/rxtx_callbacks.rst
> b/doc/guides/sample_app_ug/rxtx_callbacks.rst
> new file mode 100644
> index 0000000..9df57ed
> --- /dev/null
> +++ b/doc/guides/sample_app_ug/rxtx_callbacks.rst
> @@ -0,0 +1,251 @@
> +.. BSD LICENSE
> + Copyright(c) 2015 Intel Corporation. All rights reserved.
> + All rights reserved.
> +
> + Redistribution and use in source and binary forms, with or without
> + modification, are permitted provided that the following conditions
> + are met:
> +
> + * Redistributions of source code must retain the above copyright
> + notice, this list of conditions and the following disclaimer.
> + * Redistributions in binary form must reproduce the above copyright
> + notice, this list of conditions and the following disclaimer in
> + the documentation and/or other materials provided with the
> + distribution.
> + * Neither the name of Intel Corporation nor the names of its
> + contributors may be used to endorse or promote products derived
> + from this software without specific prior written permission.
> +
> + THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
> CONTRIBUTORS
> + "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT
> NOT
> + LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
> FITNESS FOR
> + A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
> COPYRIGHT
> + OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
> INCIDENTAL,
> + SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
> NOT
> + LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
> OF USE,
> + DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
> AND ON ANY
> + THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
> + (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
> THE USE
> + OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGE.
> +
> +
> +RX/TX Callbacks Sample Application
> +==================================
> +
> +The RX/TX Callbacks sample application is a packet forwarding
> +application that demonstrates the use of user defined callbacks on
> +received and transmitted packets. The application performs a simple
> +latency check, using callbacks, to determine the time packets spend within
> the application.
> +
> +In the sample application a user defined callback is applied to all
> +received packets to add a timestamp. A separate callback is applied to
> +all packets prior to transmission to calculate the elapsed time, in CPU
> cycles.
> +
> +
> +Compiling the Application
> +-------------------------
> +
> +To compile the application export the path to the DPDK source tree and
> +go to the example directory:
> +
> +.. code-block:: console
> +
> + export RTE_SDK=/path/to/rte_sdk
> +
> + cd ${RTE_SDK}/examples/rxtx_callbacks
> +
> +
> +Set the target, for example:
> +
> +.. code-block:: console
> +
> + export RTE_TARGET=x86_64-native-linuxapp-gcc
> +
> +See the *DPDK Getting Started* Guide for possible ``RTE_TARGET`` values.
> +
> +The callbacks feature requires that the
> +``CONFIG_RTE_ETHDEV_RXTX_CALLBACKS``
> +setting is on in the ``config/common_`` config file that applies to the
> +target. This is generally on by default:
> +
> +.. code-block:: console
> +
> + CONFIG_RTE_ETHDEV_RXTX_CALLBACKS=y
> +
> +Build the application as follows:
> +
> +.. code-block:: console
> +
> + make
> +
> +
> +Running the Application
> +-----------------------
> +
> +To run the example in a ``linuxapp`` environment:
> +
> +.. code-block:: console
> +
> + ./build/rxtx_callbacks -c 2 -n 4
> +
> +Refer to *DPDK Getting Started Guide* for general information on
> +running applications and the Environment Abstraction Layer (EAL) options.
> +
> +
> +
> +Explanation
> +-----------
> +
> +The ``rxtx_callbacks`` application is mainly a simple forwarding
> +application based on the :doc:`skeleton`. See that section of the
> +documentation for more details of the forwarding part of the application.
> +
> +The sections below explain the additional RX/TX callback code.
> +
> +
> +The Main Function
> +~~~~~~~~~~~~~~~~~
> +
> +The ``main()`` function performs the application initialization and
> +calls the execution threads for each lcore. This function is
> +effectively identical to the ``main()`` function explained in
> :doc:`skeleton`.
> +
> +The ``lcore_main()`` function is also identical.
> +
> +The main difference is in the user defined ``port_init()`` function
> +where the callbacks are added. This is explained in the next section:
> +
> +
> +The Port Initialization Function
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The main functional part of the port initialization is shown below with
> +comments:
> +
> +.. code-block:: c
> +
> + static inline int
> + port_init(uint8_t port, struct rte_mempool *mbuf_pool)
> + {
> + struct rte_eth_conf port_conf = port_conf_default;
> + const uint16_t rx_rings = 1, tx_rings = 1;
> + struct ether_addr addr;
> + int retval;
> + uint16_t q;
> +
> + if (port >= rte_eth_dev_count())
> + return -1;
> +
> + /* Configure the Ethernet device. */
> + retval = rte_eth_dev_configure(port, rx_rings, tx_rings, &port_conf);
> + if (retval != 0)
> + return retval;
> +
> + /* Allocate and set up 1 RX queue per Ethernet port. */
> + for (q = 0; q < rx_rings; q++) {
> + retval = rte_eth_rx_queue_setup(port, q, RX_RING_SIZE,
> + rte_eth_dev_socket_id(port), NULL, mbuf_pool);
> + if (retval < 0)
> + return retval;
> + }
> +
> + /* Allocate and set up 1 TX queue per Ethernet port. */
> + for (q = 0; q < tx_rings; q++) {
> + retval = rte_eth_tx_queue_setup(port, q, TX_RING_SIZE,
> + rte_eth_dev_socket_id(port), NULL);
> + if (retval < 0)
> + return retval;
> + }
> +
> + /* Start the Ethernet port. */
> + retval = rte_eth_dev_start(port);
> + if (retval < 0)
> + return retval;
> +
> + /* Enable RX in promiscuous mode for the Ethernet device. */
> + rte_eth_promiscuous_enable(port);
> +
> +
> + /* Add the callbacks for RX and TX.*/
> + rte_eth_add_rx_callback(port, 0, add_timestamps, NULL);
> + rte_eth_add_tx_callback(port, 0, calc_latency, NULL);
> +
> + return 0;
> + }
> +
> +
> +The RX and TX callbacks are added to the ports/queues as function pointers:
> +
> +.. code-block:: c
> +
> + rte_eth_add_rx_callback(port, 0, add_timestamps, NULL);
> + rte_eth_add_tx_callback(port, 0, calc_latency, NULL);
> +
> +More than one callback can be added and additional information can be
> +passed to callback function pointers as a ``void*``. In the examples
> +above ``NULL`` is used.
> +
> +The ``add_timestamps()`` and ``calc_latency()`` functions are explained
> below.
> +
> +
> +The add_timestamps() Callback
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The ``add_timestamps()`` callback is added to the RX port and is
> +applied to all packets received:
> +
> +.. code-block:: c
> +
> + static uint16_t
> + add_timestamps(uint8_t port __rte_unused, uint16_t qidx
> __rte_unused,
> + struct rte_mbuf **pkts, uint16_t nb_pkts, void *_ __rte_unused)
> + {
> + unsigned i;
> + uint64_t now = rte_rdtsc();
> +
> + for (i = 0; i < nb_pkts; i++)
> + pkts[i]->udata64 = now;
> +
> + return nb_pkts;
> + }
> +
> +The DPDK function ``rte_rdtsc()`` is used to add a cycle count
> +timestamp to each packet (see the *cycles* section of the *DPDK API
> +Documentation* for details).
> +
> +
> +The calc_latency() Callback
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The ``calc_latency()`` callback is added to the TX port and is applied
> +to all packets prior to transmission:
> +
> +.. code-block:: c
> +
> + static uint16_t
> + calc_latency(uint8_t port __rte_unused, uint16_t qidx __rte_unused,
> + struct rte_mbuf **pkts, uint16_t nb_pkts, void *_ __rte_unused)
> + {
> + uint64_t cycles = 0;
> + uint64_t now = rte_rdtsc();
> + unsigned i;
> +
> + for (i = 0; i < nb_pkts; i++)
> + cycles += now - pkts[i]->udata64;
> +
> + latency_numbers.total_cycles += cycles;
> + latency_numbers.total_pkts += nb_pkts;
> +
> + if (latency_numbers.total_pkts > (100 * 1000 * 1000ULL)) {
> + printf("Latency = %"PRIu64" cycles\n",
> + latency_numbers.total_cycles /
> + latency_numbers.total_pkts);
> +
> + latency_numbers.total_cycles = latency_numbers.total_pkts = 0;
> + }
> +
> + return nb_pkts;
> + }
> +
> +The ``calc_latency()`` function accumulates the total number of packets
> +and the total number of cycles used. Once more than 100 million packets
> +have been transmitted the average cycle count per packet is printed out
> +and the counters are reset.
> --
> 1.7.4.1
Acked-by: Siobhan Butler <siobhan.a.butler at intel.com>
