ftrace: add a script to produce a hierarchical view of a function trace

This script parses a function trace and then produces a hierarchical
view of the function call stack after processing it into a tree.

Changes on V2 thanks to the trace sent by Steven:

- Support both the files "trace" and "trace_pipe" (comments and space
  differences)

- Correct the mini HOW-TO at the beginning.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 130 insertions, 0 deletions

diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
new file mode 100644
index 000000000000..902f9a992620
--- /dev/null
+++ b/scripts/tracing/draw_functrace.py
@@ -0,0 +1,130 @@
+#!/usr/bin/python
+
+"""
+Copyright 2008 (c) Frederic Weisbecker <fweisbec@gmail.com>
+Licensed under the terms of the GNU GPL License version 2
+
+This script parses a trace provided by the function tracer in
+kernel/trace/trace_functions.c
+The resulted trace is processed into a tree to produce a more human
+view of the call stack by drawing textual but hierarchical tree of
+calls. Only the functions's names and the the call time are provided.
+
+Usage:
+        Be sure that you have CONFIG_FUNCTION_TRACER
+        # mkdir /debugfs
+        # mount -t debug debug /debug
+        # echo function > /debug/tracing/current_tracer
+        $ cat /debug/tracing/trace_pipe > ~/raw_trace_func
+        Wait some times but not too much, the script is a bit slow.
+        Break the pipe (Ctrl + Z)
+        $ scripts/draw_functrace.py < raw_trace_func > draw_functrace
+        Then you have your drawn trace in draw_functrace
+"""
+
+
+import sys, re
+
+class CallTree:
+        """ This class provides a tree representation of the functions
+                call stack. If a function has no parent in the kernel (interrupt,
+                syscall, kernel thread...) then it is attached to a virtual parent
+                called ROOT.
+        """
+        ROOT = None
+
+        def __init__(self, func, time = None, parent = None):
+                self._func = func
+                self._time = time
+                if parent is None:
+                        self._parent = CallTree.ROOT
+                else:
+                        self._parent = parent
+                self._children = []
+
+        def calls(self, func, calltime):
+                """ If a function calls another one, call this method to insert it
+                        into the tree at the appropriate place.
+                        @return: A reference to the newly created child node.
+                """
+                child = CallTree(func, calltime, self)
+                self._children.append(child)
+                return child
+
+        def getParent(self, func):
+                """ Retrieve the last parent of the current node that
+                        has the name given by func. If this function is not
+                        on a parent, then create it as new child of root
+                        @return: A reference to the parent.
+                """
+                tree = self
+                while tree != CallTree.ROOT and tree._func != func:
+                        tree = tree._parent
+                if tree == CallTree.ROOT:
+                        child = CallTree.ROOT.calls(func, None)
+                        return child
+                return tree
+
+        def __repr__(self):
+                return self.__toString("", True)
+
+        def __toString(self, branch, lastChild):
+                if self._time is not None:
+                        s = "%s----%s (%s)\n" % (branch, self._func, self._time)
+                else:
+                        s = "%s----%s\n" % (branch, self._func)
+
+                i = 0
+                if lastChild:
+                        branch = branch[:-1] + " "
+                while i < len(self._children):
+                        if i != len(self._children) - 1:
+                                s += "%s" % self._children[i].__toString(branch +\
+                                                                "    |", False)
+                        else:
+                                s += "%s" % self._children[i].__toString(branch +\
+                                                                "    |", True)
+                        i += 1
+                return s
+
+class BrokenLineException(Exception):
+        """If the last line is not complete because of the pipe breakage,
+           we want to stop the processing and ignore this line.
+        """
+        pass
+
+class CommentLineException(Exception):
+        """ If the line is a comment (as in the beginning of the trace file),
+            just ignore it.
+        """
+        pass
+
+
+def parseLine(line):
+        line = line.strip()
+        if line.startswith("#"):
+                raise CommentLineException
+        m = re.match("[^]]+?\\] +([0-9.]+): (\\w+) <-(\\w+)", line)
+        if m is None:
+                raise BrokenLineException
+        return (m.group(1), m.group(2), m.group(3))
+
+
+def main():
+        CallTree.ROOT = CallTree("Root (Nowhere)", None, None)
+        tree = CallTree.ROOT
+
+        for line in sys.stdin:
+                try:
+                        calltime, callee, caller = parseLine(line)
+                except BrokenLineException:
+                        break
+                except CommentLineException:
+                        continue
+                tree = tree.getParent(caller)
+                tree = tree.calls(callee, calltime)
+
+        print CallTree.ROOT
+
+if __name__ == "__main__":
+        main()