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>

diff --git a/scripts/tracing/draw_functrace.py b/scripts/tracing/draw_functrace.py
new file mode 100644 (file)
index 0000000..902f9a9
--- /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()