.. _section-overview:

Overview
========

The publishing side of the test writes data as fast as it can. Every few
samples (configured through the command line), it sends a special sample
requesting an echo from the subscribing side. It uses this
``request -> echo`` exchange to measure round-trip latency.

.. figure:: _static/PerfTest_Overview_Diagram.png
   :alt: PerfTest Overview Diagram

   PerfTest Overview Diagram

As you will see in Section 8, there are several command-line options,
including ones to designate whether the application will act as the
publisher or subscriber.

You will start multiple copies of the application (typically 1 publisher
and 1 or more subscribers):

-  The publishing application publishes throughput data; it also
   subscribes to the latency echoes.
-  The subscribing applications subscribe to the throughput data, in
   which the echo requests are embedded; they also publish the latency
   echoes.

The publisher prints the latency test results meanwhile the subscriber
prints the throughput results.