35b09d76f8
The coremask option in DPDK is difficult to use and we should be promoting the use of the corelist (-l) option. The patch adjusts the docs to use -l EAL option instead of the -c option. The patch only changes the docs and not the code as the -c option will continue to exist unless it is removed in the future. The -c option should be kept to maintain backward compatibility. Signed-off-by: Keith Wiles <keith.wiles@intel.com> Acked-by: John McNamara <john.mcnamara@intel.com>
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6.8 KiB
ReStructuredText
221 lines
6.8 KiB
ReStructuredText
.. BSD LICENSE
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Copyright(c) 2010-2014 Intel Corporation. All rights reserved.
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of Intel Corporation nor the names of its
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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Timer Sample Application
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========================
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The Timer sample application is a simple application that demonstrates the use of a timer in a DPDK application.
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This application prints some messages from different lcores regularly, demonstrating the use of timers.
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Compiling the Application
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-------------------------
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#. Go to the example directory:
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.. code-block:: console
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export RTE_SDK=/path/to/rte_sdk
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cd ${RTE_SDK}/examples/timer
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#. Set the target (a default target is used if not specified). For example:
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.. code-block:: console
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export RTE_TARGET=x86_64-native-linuxapp-gcc
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See the *DPDK Getting Started Guide* for possible *RTE_TARGET* values.
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#. Build the application:
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.. code-block:: console
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make
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Running the Application
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-----------------------
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To run the example in linuxapp environment:
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.. code-block:: console
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$ ./build/timer -l 0-3 -n 4
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Refer to the *DPDK Getting Started Guide* for general information on running applications and
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the Environment Abstraction Layer (EAL) options.
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Explanation
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-----------
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The following sections provide some explanation of the code.
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Initialization and Main Loop
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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In addition to EAL initialization, the timer subsystem must be initialized, by calling the rte_timer_subsystem_init() function.
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.. code-block:: c
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/* init EAL */
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ret = rte_eal_init(argc, argv);
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if (ret < 0)
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rte_panic("Cannot init EAL\n");
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/* init RTE timer library */
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rte_timer_subsystem_init();
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After timer creation (see the next paragraph),
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the main loop is executed on each slave lcore using the well-known rte_eal_remote_launch() and also on the master.
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.. code-block:: c
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/* call lcore_mainloop() on every slave lcore */
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RTE_LCORE_FOREACH_SLAVE(lcore_id) {
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rte_eal_remote_launch(lcore_mainloop, NULL, lcore_id);
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}
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/* call it on master lcore too */
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(void) lcore_mainloop(NULL);
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The main loop is very simple in this example:
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.. code-block:: c
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while (1) {
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/*
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* Call the timer handler on each core: as we don't
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* need a very precise timer, so only call
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* rte_timer_manage() every ~10ms (at 2 GHz). In a real
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* application, this will enhance performances as
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* reading the HPET timer is not efficient.
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*/
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cur_tsc = rte_rdtsc();
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diff_tsc = cur_tsc - prev_tsc;
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if (diff_tsc > TIMER_RESOLUTION_CYCLES) {
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rte_timer_manage();
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prev_tsc = cur_tsc;
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}
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}
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As explained in the comment, it is better to use the TSC register (as it is a per-lcore register) to check if the
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rte_timer_manage() function must be called or not.
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In this example, the resolution of the timer is 10 milliseconds.
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Managing Timers
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~~~~~~~~~~~~~~~
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In the main() function, the two timers are initialized.
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This call to rte_timer_init() is necessary before doing any other operation on the timer structure.
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.. code-block:: c
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/* init timer structures */
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rte_timer_init(&timer0);
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rte_timer_init(&timer1);
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Then, the two timers are configured:
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* The first timer (timer0) is loaded on the master lcore and expires every second.
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Since the PERIODICAL flag is provided, the timer is reloaded automatically by the timer subsystem.
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The callback function is timer0_cb().
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* The second timer (timer1) is loaded on the next available lcore every 333 ms.
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The SINGLE flag means that the timer expires only once and must be reloaded manually if required.
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The callback function is timer1_cb().
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.. code-block:: c
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/* load timer0, every second, on master lcore, reloaded automatically */
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hz = rte_get_hpet_hz();
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lcore_id = rte_lcore_id();
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rte_timer_reset(&timer0, hz, PERIODICAL, lcore_id, timer0_cb, NULL);
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/* load timer1, every second/3, on next lcore, reloaded manually */
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lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
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rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
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The callback for the first timer (timer0) only displays a message until a global counter reaches 20 (after 20 seconds).
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In this case, the timer is stopped using the rte_timer_stop() function.
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.. code-block:: c
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/* timer0 callback */
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static void
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timer0_cb( attribute ((unused)) struct rte_timer *tim, __attribute ((unused)) void *arg)
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{
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static unsigned counter = 0;
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unsigned lcore_id = rte_lcore_id();
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printf("%s() on lcore %u\n", FUNCTION , lcore_id);
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/* this timer is automatically reloaded until we decide to stop it, when counter reaches 20. */
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if ((counter ++) == 20)
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rte_timer_stop(tim);
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}
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The callback for the second timer (timer1) displays a message and reloads the timer on the next lcore, using the
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rte_timer_reset() function:
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.. code-block:: c
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/* timer1 callback */
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static void
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timer1_cb( attribute ((unused)) struct rte_timer *tim, _attribute ((unused)) void *arg)
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{
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unsigned lcore_id = rte_lcore_id();
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uint64_t hz;
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printf("%s() on lcore %u\\n", FUNCTION , lcore_id);
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/* reload it on another lcore */
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hz = rte_get_hpet_hz();
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lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
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rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
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}
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