X-Git-Url: http://git.droids-corp.org/?a=blobdiff_plain;f=doc%2Fguides%2Fprog_guide%2Fmetrics_lib.rst;h=eca855d60185f57a8468ad990788e65f9ce13c12;hb=2a0b41984c7ee304a86f0799b1388d7674694296;hp=71c3a1bfe883a3b0a726d6fe61edb813e3bb4fd8;hpb=2ad7ba9a6567029c2e497e8b61df96d7b911c70f;p=dpdk.git

diff --git a/doc/guides/prog_guide/metrics_lib.rst b/doc/guides/prog_guide/metrics_lib.rst
index 71c3a1bfe8..eca855d601 100644
--- a/doc/guides/prog_guide/metrics_lib.rst
+++ b/doc/guides/prog_guide/metrics_lib.rst
@@ -1,32 +1,5 @@
-..  BSD LICENSE
-    Copyright(c) 2017 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.
+..  SPDX-License-Identifier: BSD-3-Clause
+    Copyright(c) 2017 Intel Corporation.
 
 .. _Metrics_Library:
 
@@ -52,7 +25,7 @@ individual device. Since the metrics library is self-contained, the only
 restriction on port numbers is that they are less than ``RTE_MAX_ETHPORTS``
 - there is no requirement for the ports to actually exist.
 
-Initialising the library
+Initializing the library
 ------------------------
 
 Before the library can be used, it has to be initialized by calling
@@ -144,6 +117,7 @@ print out all metrics for a given port:
 .. code-block:: c
 
     void print_metrics() {
+        struct rte_metric_value *metrics;
         struct rte_metric_name *names;
         int len;
 
@@ -180,6 +154,20 @@ print out all metrics for a given port:
     }
 
 
+Deinitialising the library
+--------------------------
+
+Once the library usage is done, it must be deinitialized by calling
+``rte_metrics_deinit()`` which will free the shared memory reserved
+during initialization.
+
+.. code-block:: c
+
+    err = rte_metrics_deinit(void);
+
+If the return value is negative, it means deinitialization failed.
+This function **must** be called from a primary process.
+
 Bit-rate statistics library
 ---------------------------
 
@@ -243,3 +231,66 @@ desired, this function should be called once a second.
 	    }
         /* ... */
     }
+
+
+Latency statistics library
+--------------------------
+
+The latency statistics library calculates the latency of packet
+processing by a DPDK application, reporting the minimum, average,
+and maximum nano-seconds that packet processing takes, as well as
+the jitter in processing delay. These statistics are then reported
+via the metrics library using the following names:
+
+    - ``min_latency_ns``: Minimum processing latency (nano-seconds)
+    - ``avg_latency_ns``:  Average  processing latency (nano-seconds)
+    - ``mac_latency_ns``:  Maximum  processing latency (nano-seconds)
+    - ``jitter_ns``: Variance in processing latency (nano-seconds)
+
+Once initialised and clocked at the appropriate frequency, these
+statistics can be obtained by querying the metrics library.
+
+Initialization
+~~~~~~~~~~~~~~
+
+Before the library can be used, it has to be initialised by calling
+``rte_latencystats_init()``.
+
+.. code-block:: c
+
+    lcoreid_t latencystats_lcore_id = -1;
+
+    int ret = rte_latencystats_init(1, NULL);
+    if (ret)
+        rte_exit(EXIT_FAILURE, "Could not allocate latency data.\n");
+
+
+Triggering statistic updates
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The ``rte_latencystats_update()`` function needs to be called
+periodically so that latency statistics can be updated.
+
+.. code-block:: c
+
+    if (latencystats_lcore_id == rte_lcore_id())
+        rte_latencystats_update();
+
+Library shutdown
+~~~~~~~~~~~~~~~~
+
+When finished, ``rte_latencystats_uninit()`` needs to be called to
+de-initialise the latency library.
+
+.. code-block:: c
+
+    rte_latencystats_uninit();
+
+Timestamp and latency calculation
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Latency stats library marks the time in the timestamp field of the
+mbuf for the ingress packets and sets the ``PKT_RX_TIMESTAMP`` flag of
+``ol_flags`` for the mbuf to indicate the marked time as a valid one.
+At the egress, the mbufs with the flag set are considered having valid
+timestamp and are used for the latency calculation.