linux-kernel - [PATCH] ftrace: add documentation for trace commands mod, traceon/traceoff

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Message-Id: <1272045759-32018-1-git-send-email-chase.douglas@canonical.com>
Date:	Fri, 23 Apr 2010 14:02:39 -0400
From:	Chase Douglas <chase.douglas@...onical.com>
To:	linux-kernel@...r.kernel.org
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>
Subject: [PATCH] ftrace: add documentation for trace commands mod, traceon/traceoff

The mod command went in as commit
64e7c440618998fd69eee6ab490b042d12248021

The traceon/traceoff commands went in as commit
23b4ff3aa479c9e3bb23cb6b2d0a97878399784a

Signed-off-by: Chase Douglas <chase.douglas@...onical.com>
---
 Documentation/trace/ftrace.txt |   44 ++++++++++++++++++++++++++++++++++++++++
 1 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 03485bf..8105e16 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -155,6 +155,9 @@ of ftrace. Here is a list of some of the key files:
 	to be traced. Echoing names of functions into this file
 	will limit the trace to only those functions.
 
+	This interface also allows for commands to be used. See the
+	"Filter commands" section for more details.
+
   set_ftrace_notrace:
 
 	This has an effect opposite to that of
@@ -1822,6 +1825,47 @@ this special filter via:
  echo > set_graph_function
 
 
+Filter commands
+---------------
+
+A few commands are supported by the set_ftrace_filter interface.
+Trace commands have the following format:
+
+<function>:<command>:<parameter>
+
+The following commands are supported:
+
+- mod
+  This command enables function filtering per module. The
+  parameter defines the module. For example, if only the write*
+  functions in the ext3 module are desired, run:
+
+   echo 'write*:mod:ext3' > set_ftrace_filter
+
+  This command interacts with the filter in the same way as
+  filtering based on function names. Thus, adding more functions
+  in a different module is accomplished by appending (>>) to the
+  filter file. Remove specific module functions by prepending
+  '!':
+
+   echo '!writeback*:mod:ext3' >> set_ftrace_filter
+
+- traceon/traceoff
+  These commands turn tracing on and off when the specified
+  functions are hit. The parameter determines how many times the
+  tracing system is turned on and off. If unspecified, there is
+  no limit. For example, to disable tracing when a schedule bug
+  is hit the first 5 times, run:
+
+   echo '__schedule_bug:traceoff:5' > set_ftrace_filter
+
+  These commands are cumulative whether or not they are appended
+  to set_ftrace_filter. To remove a command, prepend it by '!'
+  and drop the parameter:
+
+   echo '!__schedule_bug:traceoff' > set_ftrace_filter
+
+
 trace_pipe
 ----------
 
-- 
1.7.0

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