scripts/show_delta

#!/usr/bin/env python3
# SPDX-License-Identifier: GPL-2.0-only
#
# show_deltas: Read list of printk messages instrumented with
# time data, and format with time deltas.
#
# Also, you can show the times relative to a fixed point.
#
# Copyright 2003 Sony Corporation
#

import sys
import string

def usage():
	print ("""usage: show_delta [<options>] <filename>

This program parses the output from a set of printk message lines which
have time data prefixed because the CONFIG_PRINTK_TIME option is set, or
the kernel command line option "time" is specified. When run with no
options, the time information is converted to show the time delta between
each printk line and the next.  When run with the '-b' option, all times
are relative to a single (base) point in time.

Options:
  -h            Show this usage help.
  -b <base>	Specify a base for time references.
		<base> can be a number or a string.
		If it is a string, the first message line
		which matches (at the beginning of the
		line) is used as the time reference.

ex: $ dmesg >timefile
    $ show_delta -b NET4 timefile

will show times relative to the line in the kernel output
starting with "NET4".
""")
	sys.exit(1)

# returns a tuple containing the seconds and text for each message line
# seconds is returned as a float
# raise an exception if no timing data was found
def get_time(line):
	if line[0]!="[":
		raise ValueError

	# split on closing bracket
	(time_str, rest) = string.split(line[1:],']',1)
	time = string.atof(time_str)

	#print "time=", time
	return (time, rest)


# average line looks like:
# [    0.084282] VFS: Mounted root (romfs filesystem) readonly
# time data is expressed in seconds.useconds,
# convert_line adds a delta for each line
last_time = 0.0
def convert_line(line, base_time):
	global last_time

	try:
		(time, rest) = get_time(line)
	except:
		# if any problem parsing time, don't convert anything
		return line

	if base_time:
		# show time from base
		delta = time - base_time
	else:
		# just show time from last line
		delta = time - last_time
		last_time = time

	return ("[%5.6f < %5.6f >]" % (time, delta)) + rest

def main():
	base_str = ""
	filein = ""
	for arg in sys.argv[1:]:
		if arg=="-b":
			base_str = sys.argv[sys.argv.index("-b")+1]
		elif arg=="-h":
			usage()
		else:
			filein = arg

	if not filein:
		usage()

	try:
		lines = open(filein,"r").readlines()
	except:
		print ("Problem opening file: %s" % filein)
		sys.exit(1)

	if base_str:
		print ('base= "%s"' % base_str)
		# assume a numeric base.  If that fails, try searching
		# for a matching line.
		try:
			base_time = float(base_str)
		except:
			# search for line matching <base> string
			found = 0
			for line in lines:
				try:
					(time, rest) = get_time(line)
				except:
					continue
				if string.find(rest, base_str)==1:
					base_time = time
					found = 1
					# stop at first match
					break
			if not found:
				print ('Couldn\'t find line matching base pattern "%s"' % base_str)
				sys.exit(1)
	else:
		base_time = 0.0

	for line in lines:
		print (convert_line(line, base_time),)

if __name__ == "__main__":
	main()