1 files changed, 220 insertions, 0 deletions
diff --git a/doc/guides/sample_app_ug/timer.rst b/doc/guides/sample_app_ug/timer.rst
new file mode 100644
index 00000000..e4de359d
--- /dev/null
+++ b/doc/guides/sample_app_ug/timer.rst
@@ -0,0 +1,220 @@
+..  BSD LICENSE
+    Copyright(c) 2010-2014 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.
+
+Timer Sample Application
+========================
+
+The Timer sample application is a simple application that demonstrates the use of a timer in a DPDK application.
+This application prints some messages from different lcores regularly, demonstrating the use of timers.
+
+Compiling the Application
+-------------------------
+
+#.  Go to the example directory:
+
+    .. code-block:: console
+
+        export RTE_SDK=/path/to/rte_sdk
+        cd ${RTE_SDK}/examples/timer
+
+#.  Set the target (a default target is used if not specified). For example:
+
+    .. code-block:: console
+
+        export RTE_TARGET=x86_64-native-linuxapp-gcc
+
+    See the *DPDK Getting Started Guide* for possible *RTE_TARGET* values.
+
+#.  Build the application:
+
+    .. code-block:: console
+
+        make
+
+Running the Application
+-----------------------
+
+To run the example in linuxapp environment:
+
+.. code-block:: console
+
+    $ ./build/timer -c f -n 4
+
+Refer to the *DPDK Getting Started Guide* for general information on running applications and
+the Environment Abstraction Layer (EAL) options.
+
+Explanation
+-----------
+
+The following sections provide some explanation of the code.
+
+Initialization and Main Loop
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+In addition to EAL initialization, the timer subsystem must be initialized, by calling the rte_timer_subsystem_init() function.
+
+.. code-block:: c
+
+    /* init EAL */
+
+    ret = rte_eal_init(argc, argv);
+    if (ret < 0)
+        rte_panic("Cannot init EAL\n");
+
+    /* init RTE timer library */
+
+    rte_timer_subsystem_init();
+
+After timer creation (see the next paragraph),
+the main loop is executed on each slave lcore using the well-known rte_eal_remote_launch() and also on the master.
+
+.. code-block:: c
+
+    /* call lcore_mainloop() on every slave lcore  */
+
+    RTE_LCORE_FOREACH_SLAVE(lcore_id) {
+        rte_eal_remote_launch(lcore_mainloop, NULL, lcore_id);
+    }
+
+    /* call it on master lcore too */
+
+    (void) lcore_mainloop(NULL);
+
+The main loop is very simple in this example:
+
+.. code-block:: c
+
+    while (1) {
+        /*
+         *   Call the timer handler on each core: as we don't
+         *   need a very precise timer, so only call
+         *   rte_timer_manage() every ~10ms (at 2 GHz). In a real
+         *   application, this will enhance performances as
+         *   reading the HPET timer is not efficient.
+        */
+
+        cur_tsc = rte_rdtsc();
+
+        diff_tsc = cur_tsc - prev_tsc;
+
+        if (diff_tsc > TIMER_RESOLUTION_CYCLES) {
+            rte_timer_manage();
+            prev_tsc = cur_tsc;
+        }
+    }
+
+As explained in the comment, it is better to use the TSC register (as it is a per-lcore register) to check if the
+rte_timer_manage() function must be called or not.
+In this example, the resolution of the timer is 10 milliseconds.
+
+Managing Timers
+~~~~~~~~~~~~~~~
+
+In the main() function, the two timers are initialized.
+This call to rte_timer_init() is necessary before doing any other operation on the timer structure.
+
+.. code-block:: c
+
+    /* init timer structures */
+
+    rte_timer_init(&timer0);
+    rte_timer_init(&timer1);
+
+Then, the two timers are configured:
+
+*   The first timer (timer0) is loaded on the master lcore and expires every second.
+    Since the PERIODICAL flag is provided, the timer is reloaded automatically by the timer subsystem.
+    The callback function is timer0_cb().
+
+*   The second timer (timer1) is loaded on the next available lcore every 333 ms.
+    The SINGLE flag means that the timer expires only once and must be reloaded manually if required.
+    The callback function is timer1_cb().
+
+.. code-block:: c
+
+    /* load timer0, every second, on master lcore, reloaded automatically */
+
+    hz = rte_get_hpet_hz();
+
+    lcore_id = rte_lcore_id();
+
+    rte_timer_reset(&timer0, hz, PERIODICAL, lcore_id, timer0_cb, NULL);
+
+    /* load timer1, every second/3, on next lcore, reloaded manually */
+
+    lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
+
+    rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
+
+The callback for the first timer (timer0) only displays a message until a global counter reaches 20 (after 20 seconds).
+In this case, the timer is stopped using the rte_timer_stop() function.
+
+.. code-block:: c
+
+    /* timer0 callback */
+
+    static void
+    timer0_cb( attribute ((unused)) struct rte_timer *tim, __attribute ((unused)) void *arg)
+    {
+        static unsigned counter = 0;
+
+        unsigned lcore_id = rte_lcore_id();
+
+        printf("%s() on lcore %u\n", FUNCTION , lcore_id);
+
+        /* this timer is automatically reloaded until we decide to stop it, when counter reaches 20. */
+
+        if ((counter ++) == 20)
+            rte_timer_stop(tim);
+    }
+
+The callback for the second timer (timer1) displays a message and reloads the timer on the next lcore, using the
+rte_timer_reset() function:
+
+.. code-block:: c
+
+    /* timer1 callback */
+
+    static void
+    timer1_cb( attribute ((unused)) struct rte_timer *tim, _attribute ((unused)) void *arg)
+    {
+        unsigned lcore_id = rte_lcore_id();
+        uint64_t hz;
+
+        printf("%s() on lcore %u\\n", FUNCTION , lcore_id);
+
+        /* reload it on another lcore */
+
+        hz = rte_get_hpet_hz();
+
+        lcore_id = rte_get_next_lcore(lcore_id, 0, 1);
+
+        rte_timer_reset(&timer1, hz/3, SINGLE, lcore_id, timer1_cb, NULL);
+    }