X-Git-Url: https://gerrit.opnfv.org/gerrit/gitweb?a=blobdiff_plain;f=docs%2Ftesting%2Fuser%2Fuserguide%2Ffaq.rst;h=a8aad9adf4a1b7403c6fee570b60741d8feee456;hb=refs%2Fheads%2Fpy27;hp=9a1a7dabcb7f55ff2ec29fbd7ea9e417a6c08fd4;hpb=15ecdba939f0377c0cccaa76e5a070ef2357056b;p=nfvbench.git

diff --git a/docs/testing/user/userguide/faq.rst b/docs/testing/user/userguide/faq.rst
index 9a1a7da..a8aad9a 100644
--- a/docs/testing/user/userguide/faq.rst
+++ b/docs/testing/user/userguide/faq.rst
@@ -47,3 +47,49 @@ The most common issues that prevent traffic from passing are:
 
    - if the switch port is configured as access port, you must disable vlan_tagging in the NFVbench configuration
    - of the switch port is configured as trunk (recommended method), you must enable it
+
+Issues with high performances at a high line rate
+-------------------------------------------------
+
+Flow statistics and/or latency stream can cause performance issue when testing high line rate.
+
+Flow statistics implies CPU usage to analyse packets and retrieve statistics. CPU can reach 100% usage when high throughput is tested because only one CPU is used for packet reception in TRex.
+The ``--no-flow-stats`` option allows you to disable TRex statistics aggregation during the NFVBench test.
+This, will permit to save CPU capabilities used for packet reception.
+
+Example of use :
+
+.. code-block:: bash
+
+    nfvbench ``--no-flow-stats``
+
+    2019-10-28 10:26:52,099 INFO End-to-end connectivity established
+    2019-10-28 10:26:52,127 INFO Cleared all existing streams
+    2019-10-28 10:26:52,129 INFO Traffic flow statistics are disabled.
+
+
+Latency streams implies also CPU usage to analyse packets and retrieve latency values. CPU can reach 100% usage when high throughput is tested because only one CPU is used for packet reception in TRex.
+The ``--no-latency-streams`` option allows you to disable latency streams during the NFVBench test.
+This, will permit to save CPU capabilities used for packet reception but no latency information will be return (to be used only if latency value has no meaning for your test).
+
+Example of use :
+
+.. code-block:: bash
+
+    nfvbench ``--no-latency-streams``
+    2019-10-28 10:30:03,955 INFO End-to-end connectivity established
+    2019-10-28 10:30:03,982 INFO Cleared all existing streams
+    2019-10-28 10:30:03,982 INFO Latency streams are disabled
+
+
+Latency flow statistics implies CPU usage to analyse packets and retrieve statistics. CPU can reach 100% usage when high throughput is tested because only one CPU is used for packet reception in TRex.
+The ``--no-latency-stats`` option allows you to disable TRex statistics aggregation for latency packets during the NFVBench test.
+This, will permit to save CPU capabilities used for packet reception.
+
+Example of use :
+
+.. code-block:: bash
+
+    nfvbench ``--no-latency-stats``
+    2019-10-28 10:28:21,559 INFO Cleared all existing streams
+    2019-10-28 10:28:21,567 INFO Latency flow statistics are disabled.