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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 #. Go to the example directory:
42 .. code-block:: console
44 export RTE_SDK=/path/to/rte_sdk cd ${RTE_SDK}/examples/timer
46 #. Set the target (a default target is used if not specified). For example:
48 .. code-block:: console
50 export RTE_TARGET=x86_64-native-linuxapp-gcc
52 See the *DPDK Getting Started Guide* for possible *RTE_TARGET* values.
54 #. Build the application:
56 .. code-block:: console
60 Running the Application
61 -----------------------
63 To run the example in linuxapp environment:
65 .. code-block:: console
67 $ ./build/timer -c f -n 4
69 Refer to the *DPDK Getting Started Guide* for general information on running applications and
70 the Environment Abstraction Layer (EAL) options.
75 The following sections provide some explanation of the code.
77 Initialization and Main Loop
78 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
80 In addition to EAL initialization, the timer subsystem must be initialized, by calling the rte_timer_subsystem_init() function.
86 ret = rte_eal_init(argc, argv);
88 rte_panic("Cannot init EAL\n");
90 /* init RTE timer library */
92 rte_timer_subsystem_init();
94 After timer creation (see the next paragraph),
95 the main loop is executed on each slave lcore using the well-known rte_eal_remote_launch() and also on the master.
99 /* call lcore_mainloop() on every slave lcore */
101 RTE_LCORE_FOREACH_SLAVE(lcore_id) {
102 rte_eal_remote_launch(lcore_mainloop, NULL, lcore_id);
105 /* call it on master lcore too */
107 (void) lcore_mainloop(NULL);
109 The main loop is very simple in this example:
115 * Call the timer handler on each core: as we don't
116 * need a very precise timer, so only call
117 * rte_timer_manage() every ~10ms (at 2 GHz). In a real
118 * application, this will enhance performances as
119 * reading the HPET timer is not efficient.
122 cur_tsc = rte_rdtsc();
124 diff_tsc = cur_tsc - prev_tsc;
126 if (diff_tsc > TIMER_RESOLUTION_CYCLES) {
132 As explained in the comment, it is better to use the TSC register (as it is a per-lcore register) to check if the
133 rte_timer_manage() function must be called or not.
134 In this example, the resolution of the timer is 10 milliseconds.
139 In the main() function, the two timers are initialized.
140 This call to rte_timer_init() is necessary before doing any other operation on the timer structure.
144 /* init timer structures */
146 rte_timer_init(&timer0);
147 rte_timer_init(&timer1);
149 Then, the two timers are configured:
151 * The first timer (timer0) is loaded on the master lcore and expires every second.
152 Since the PERIODICAL flag is provided, the timer is reloaded automatically by the timer subsystem.
153 The callback function is timer0_cb().
155 * The second timer (timer1) is loaded on the next available lcore every 333 ms.
156 The SINGLE flag means that the timer expires only once and must be reloaded manually if required.
157 The callback function is timer1_cb().
161 /* load timer0, every second, on master lcore, reloaded automatically */
163 hz = rte_get_hpet_hz();
165 lcore_id = rte_lcore_id();
167 rte_timer_reset(&timer0, hz, PERIODICAL, lcore_id, timer0_cb, NULL);
169 /* load timer1, every second/3, on next lcore, reloaded manually */
171 lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
173 rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
175 The callback for the first timer (timer0) only displays a message until a global counter reaches 20 (after 20 seconds).
176 In this case, the timer is stopped using the rte_timer_stop() function.
180 /* timer0 callback */
183 timer0_cb( attribute ((unused)) struct rte_timer *tim, __attribute ((unused)) void *arg)
185 static unsigned counter = 0;
187 unsigned lcore_id = rte_lcore_id();
189 printf("%s() on lcore %u\n", FUNCTION , lcore_id);
191 /* this timer is automatically reloaded until we decide to stop it, when counter reaches 20. */
193 if ((counter ++) == 20)
197 The callback for the second timer (timer1) displays a message and reloads the timer on the next lcore, using the
198 rte_timer_reset() function:
202 /* timer1 callback */
205 timer1_cb( attribute ((unused)) struct rte_timer *tim, _attribute ((unused)) void *arg)
207 unsigned lcore_id = rte_lcore_id();
210 printf("%s() on lcore %u\\n", FUNCTION , lcore_id);
212 /* reload it on another lcore */
214 hz = rte_get_hpet_hz();
216 lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
218 rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);