[J/realtime][PATCH 12/15] rtla: Add rtla timerlat documentation

[Krzysztof Kozlowski]

From: Daniel Bristot de Oliveira <bristot at kernel.org>

BugLink: https://bugs.launchpad.net/bugs/1959130

Man page for rtla timerlat tool.

Link: https://lkml.kernel.org/r/78678b8d024bf5a3a79f831ac9441b96e8d2f56e.1639158831.git.bristot@kernel.org

Cc: Tao Zhou <tao.zhou at linux.dev>
Cc: Ingo Molnar <mingo at redhat.com>
Cc: Tom Zanussi <zanussi at kernel.org>
Cc: Masami Hiramatsu <mhiramat at kernel.org>
Cc: Juri Lelli <juri.lelli at redhat.com>
Cc: Clark Williams <williams at redhat.com>
Cc: John Kacur <jkacur at redhat.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy at linutronix.de>
Cc: Daniel Bristot de Oliveira <bristot at kernel.org>
Cc: linux-rt-users at vger.kernel.org
Cc: linux-trace-devel at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Signed-off-by: Daniel Bristot de Oliveira <bristot at kernel.org>
Signed-off-by: Steven Rostedt <rostedt at goodmis.org>
(cherry picked from commit 29380d4055e524de918c76a861df17d14a4b7224)
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski at canonical.com>
---
 .../rtla/common_timerlat_description.rst      | 10 ++++
 Documentation/tools/rtla/rtla-timerlat.rst    | 57 +++++++++++++++++++
 2 files changed, 67 insertions(+)
 create mode 100644 Documentation/tools/rtla/common_timerlat_description.rst
 create mode 100644 Documentation/tools/rtla/rtla-timerlat.rst

diff --git a/Documentation/tools/rtla/common_timerlat_description.rst b/Documentation/tools/rtla/common_timerlat_description.rst
new file mode 100644
index 000000000000..321201cb8597
--- /dev/null
+++ b/Documentation/tools/rtla/common_timerlat_description.rst
@@ -0,0 +1,10 @@
+The **rtla timerlat** tool is an interface for the *timerlat* tracer. The
+*timerlat* tracer dispatches a kernel thread per-cpu. These threads
+set a periodic timer to wake themselves up and go back to sleep. After
+the wakeup, they collect and generate useful information for the
+debugging of operating system timer latency.
+
+The *timerlat* tracer outputs information in two ways. It periodically
+prints the timer latency at the timer *IRQ* handler and the *Thread*
+handler. It also enable the trace of the most relevant information via
+**osnoise:** tracepoints.
diff --git a/Documentation/tools/rtla/rtla-timerlat.rst b/Documentation/tools/rtla/rtla-timerlat.rst
new file mode 100644
index 000000000000..44a49e6f302b
--- /dev/null
+++ b/Documentation/tools/rtla/rtla-timerlat.rst
@@ -0,0 +1,57 @@
+================
+rtla-timerlat
+================
+-------------------------------------------
+Measures the operating system timer latency
+-------------------------------------------
+
+:Manual section: 1
+
+SYNOPSIS
+========
+**rtla timerlat** [*MODE*] ...
+
+DESCRIPTION
+===========
+
+.. include:: common_timerlat_description.rst
+
+The *timerlat* tracer outputs information in two ways. It periodically
+prints the timer latency at the timer *IRQ* handler and the *Thread* handler.
+It also provides information for each noise via the **osnoise:** tracepoints.
+The **rtla timerlat top** mode displays a summary of the periodic output
+from the *timerlat* tracer. The **rtla hist hist** mode displays a histogram
+of each tracer event occurrence. For further details, please refer to the
+respective man page.
+
+MODES
+=====
+**top**
+
+        Prints the summary from *timerlat* tracer.
+
+**hist**
+
+        Prints a histogram of timerlat samples.
+
+If no *MODE* is given, the top mode is called, passing the arguments.
+
+OPTIONS
+=======
+**-h**, **--help**
+
+        Display the help text.
+
+For other options, see the man page for the corresponding mode.
+
+SEE ALSO
+========
+**rtla-timerlat-top**\(1), **rtla-timerlat-hist**\(1)
+
+*timerlat* tracer documentation: <https://www.kernel.org/doc/html/latest/trace/timerlat-tracer.html>
+
+AUTHOR
+======
+Written by Daniel Bristot de Oliveira <bristot at kernel.org>
+
+.. include:: common_appendix.rst
-- 
2.32.0