[PATCH 2/2] user: Add basic event recording documentation

[Sebastian Huber]

Update #3665.
---
 user/tracing/captureengine.rst  |  2 +-
 user/tracing/eventrecording.rst | 57 +++++++++++++++++++++++++++++++++++++++++
 user/tracing/index.rst          |  1 +
 user/tracing/introduction.rst   |  5 ++--
 user/tracing/tracelinker.rst    |  2 +-
 5 files changed, 63 insertions(+), 4 deletions(-)
 create mode 100644 user/tracing/eventrecording.rst

diff --git a/user/tracing/captureengine.rst b/user/tracing/captureengine.rst
index b976825..fab8bed 100644
--- a/user/tracing/captureengine.rst
+++ b/user/tracing/captureengine.rst
@@ -2,7 +2,7 @@
 
 .. Copyright (C) 2018 Vidushi Vashishth <vidushivashishth96 at gmail.com>
 
-.. _capturengine:
+.. _CaptureEngine:
 
 Capture Engine
 **************
diff --git a/user/tracing/eventrecording.rst b/user/tracing/eventrecording.rst
new file mode 100644
index 0000000..8627aed
--- /dev/null
+++ b/user/tracing/eventrecording.rst
@@ -0,0 +1,57 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019 embedded brains GmbH
+.. Copyright (C) 2019 Sebastian Huber
+
+.. _EventRecording:
+
+Event Recording
+===============
+
+The `event recording` support focuses on the recording of high frequency
+events such as
+
+     * thread switches,
+     * thread queue enqueue and surrender,
+     * interrupt entry and exit,
+     * heap/workspace memory allocate/free,
+     * UMA zone allocate/free,
+     * Ethernet packet input/output, and
+     * etc.
+
+There is a fixed set of 512 system reserved and 512 user defined events which
+are identified by an event number (:c:type:`rtems_record_event`).
+
+The event recording support allows post-mortem analysis in fatal error
+handlers, e.g. the last events are in the record buffers, the newest event
+overwrites the oldest event.  It is possible to detect record buffer overflows
+for consumers that expect a continuous stream of events, e.g. to display the
+system state changes in real-time.
+
+The implementation supports high-end SMP machines (more than 1GHz processor
+frequency, more than four processors).  It uses per-processor ring buffers to
+record the events.  Synchronization is done without atomic read-modify-write
+operations.  The CPU counter is used to get the time of events. It is combined
+with periodic uptime events to synchronize it with CLOCK_MONOTONIC.
+
+The application must configure the event recording via the configuration options
+:c:macro:`CONFIGURE_RECORD_PER_PROCESSOR_ITEMS` and
+:c:macro:`CONFIGURE_RECORD_EXTENSIONS_ENABLED`.
+
+Events can be recorded for example with the :c:func:`rtems_record_produce`
+function.
+
+.. code-block:: c
+
+    #include <rtems/record.h>
+
+    void f( void )
+    {
+        rtems_record_produce( RTEMS_RECORD_USER( 0 ), 123 );
+    }
+
+Recorded events can be sent to a host computer with a very simple record server
+started by :c:func:`rtems_record_start_server` via a TCP connection.
+
+On the host computer you may use the command line tool :file:`rtems-record` to
+get recorded events from the record server running on the target system.
diff --git a/user/tracing/index.rst b/user/tracing/index.rst
index 3f0c90b..ed9028a 100644
--- a/user/tracing/index.rst
+++ b/user/tracing/index.rst
@@ -26,3 +26,4 @@ the code from the source and without annotating the source with trace code.
    examples
    captureengine
    tracelinker
+   eventrecording
diff --git a/user/tracing/introduction.rst b/user/tracing/introduction.rst
index a3b4904..d6f249f 100644
--- a/user/tracing/introduction.rst
+++ b/user/tracing/introduction.rst
@@ -17,8 +17,9 @@ RTEMS tracing framework is under development and welcomes contribution by users.
 
 RTEMS has the following trace components:
 
-- RTEMS :ref:`tracelinker`
-- RTEMS :ref:`capturengine`
+- :ref:`RTEMS Trace Linker <TraceLinker>`
+- :ref:`RTEMS Capture Engine <CaptureEngine>`
+- :ref:`RTEMS Event Recording <EventRecording>`
 - Common Trace Format Integration
 
 RTEMS trace framework can currently function using the following methods. Both
diff --git a/user/tracing/tracelinker.rst b/user/tracing/tracelinker.rst
index 0fd1757..8aad20f 100644
--- a/user/tracing/tracelinker.rst
+++ b/user/tracing/tracelinker.rst
@@ -2,7 +2,7 @@
 
 .. Copyright (C) 2016 Chris Johns <chrisj at rtems.org>
 
-.. _tracelinker:
+.. _TraceLinker:
 
 Trace Linker
 ************
-- 
2.16.4