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31 Timer Sample Application
32 ========================
34 The Timer sample application is a simple application that demonstrates the use of a timer in a DPDK application.
35 This application prints some messages from different lcores regularly, demonstrating the use of timers.
37 Compiling the Application
38 -------------------------
40 To compile the sample application see :doc:`compiling`.
42 The application is located in the ``timer`` sub-directory.
44 Running the Application
45 -----------------------
47 To run the example in linuxapp environment:
49 .. code-block:: console
51 $ ./build/timer -l 0-3 -n 4
53 Refer to the *DPDK Getting Started Guide* for general information on running applications and
54 the Environment Abstraction Layer (EAL) options.
59 The following sections provide some explanation of the code.
61 Initialization and Main Loop
62 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
64 In addition to EAL initialization, the timer subsystem must be initialized, by calling the rte_timer_subsystem_init() function.
70 ret = rte_eal_init(argc, argv);
72 rte_panic("Cannot init EAL\n");
74 /* init RTE timer library */
76 rte_timer_subsystem_init();
78 After timer creation (see the next paragraph),
79 the main loop is executed on each slave lcore using the well-known rte_eal_remote_launch() and also on the master.
83 /* call lcore_mainloop() on every slave lcore */
85 RTE_LCORE_FOREACH_SLAVE(lcore_id) {
86 rte_eal_remote_launch(lcore_mainloop, NULL, lcore_id);
89 /* call it on master lcore too */
91 (void) lcore_mainloop(NULL);
93 The main loop is very simple in this example:
99 * Call the timer handler on each core: as we don't
100 * need a very precise timer, so only call
101 * rte_timer_manage() every ~10ms (at 2 GHz). In a real
102 * application, this will enhance performances as
103 * reading the HPET timer is not efficient.
106 cur_tsc = rte_rdtsc();
108 diff_tsc = cur_tsc - prev_tsc;
110 if (diff_tsc > TIMER_RESOLUTION_CYCLES) {
116 As explained in the comment, it is better to use the TSC register (as it is a per-lcore register) to check if the
117 rte_timer_manage() function must be called or not.
118 In this example, the resolution of the timer is 10 milliseconds.
123 In the main() function, the two timers are initialized.
124 This call to rte_timer_init() is necessary before doing any other operation on the timer structure.
128 /* init timer structures */
130 rte_timer_init(&timer0);
131 rte_timer_init(&timer1);
133 Then, the two timers are configured:
135 * The first timer (timer0) is loaded on the master lcore and expires every second.
136 Since the PERIODICAL flag is provided, the timer is reloaded automatically by the timer subsystem.
137 The callback function is timer0_cb().
139 * The second timer (timer1) is loaded on the next available lcore every 333 ms.
140 The SINGLE flag means that the timer expires only once and must be reloaded manually if required.
141 The callback function is timer1_cb().
145 /* load timer0, every second, on master lcore, reloaded automatically */
147 hz = rte_get_hpet_hz();
149 lcore_id = rte_lcore_id();
151 rte_timer_reset(&timer0, hz, PERIODICAL, lcore_id, timer0_cb, NULL);
153 /* load timer1, every second/3, on next lcore, reloaded manually */
155 lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
157 rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
159 The callback for the first timer (timer0) only displays a message until a global counter reaches 20 (after 20 seconds).
160 In this case, the timer is stopped using the rte_timer_stop() function.
164 /* timer0 callback */
167 timer0_cb( attribute ((unused)) struct rte_timer *tim, __attribute ((unused)) void *arg)
169 static unsigned counter = 0;
171 unsigned lcore_id = rte_lcore_id();
173 printf("%s() on lcore %u\n", FUNCTION , lcore_id);
175 /* this timer is automatically reloaded until we decide to stop it, when counter reaches 20. */
177 if ((counter ++) == 20)
181 The callback for the second timer (timer1) displays a message and reloads the timer on the next lcore, using the
182 rte_timer_reset() function:
186 /* timer1 callback */
189 timer1_cb( attribute ((unused)) struct rte_timer *tim, _attribute ((unused)) void *arg)
191 unsigned lcore_id = rte_lcore_id();
194 printf("%s() on lcore %u\\n", FUNCTION , lcore_id);
196 /* reload it on another lcore */
198 hz = rte_get_hpet_hz();
200 lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
202 rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);