bindings/python/examples/sched_switch.py

   1 #!/usr/bin/env python3
   2 # sched_switch.py
   3 #
   4 # Babeltrace example script with sched_switch events
   5 #
   6 # Copyright 2012 EfficiOS Inc.
   7 #
   8 # Author: Danny Serres <danny.serres@efficios.com>
   9 #
  10 # Permission is hereby granted, free of charge, to any person obtaining a copy
  11 # of this software and associated documentation files (the "Software"), to deal
  12 # in the Software without restriction, including without limitation the rights
  13 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  14 # copies of the Software, and to permit persons to whom the Software is
  15 # furnished to do so, subject to the following conditions:
  16 #
  17 # The above copyright notice and this permission notice shall be included in
  18 # all copies or substantial portions of the Software.
  19
  20 # The script takes one optional argument (pid)
  21 # The script will read events based on pid and
  22 # print the scheduler switches happening with the process.
  23 # If no arguments are passed, it displays all the scheduler switches.
  24 # This can be used to understand which tasks schedule out the current
  25 # process being traced, and when it gets scheduled in again.
  26 # The trace needs PID context (lttng add-context -k -t pid)
  27
  28 import sys
  29 from babeltrace import *
  30
  31 if len(sys.argv) < 2 or len(sys.argv) > 3:
  32         raise TypeError("Usage: python sched_switch.py [pid] path/to/trace")
  33 elif len(sys.argv) == 3:
  34         usePID = True
  35 else:
  36         usePID = False
  37
  38
  39 ctx = Context()
  40 ret = ctx.add_trace(sys.argv[len(sys.argv)-1], "ctf")
  41 if ret is None:
  42         raise IOError("Error adding trace")
  43
  44 # Setting iterator
  45 bp = IterPos(SEEK_BEGIN)
  46 ctf_it = ctf.Iterator(ctx, bp)
  47
  48 # Reading events
  49 event = ctf_it.read_event()
  50 while event is not None:
  51         while True:
  52                 if event.get_name() == "sched_switch":
  53                         # Getting scope definition
  54                         sco = event.get_top_level_scope(ctf.scope.STREAM_EVENT_CONTEXT)
  55                         if sco is None:
  56                                 print("ERROR: Cannot get definition scope for sched_switch")
  57                                 break # Next event
  58
  59                         # Getting PID
  60                         pid_field = event.get_field(sco, "_pid")
  61                         pid = pid_field.get_int64()
  62
  63                         if ctf.field_error():
  64                                 print("ERROR: Missing PID info for sched_switch")
  65                                 break # Next event
  66
  67                         if usePID and (pid != long(sys.argv[1])):
  68                                 break # Next event
  69
  70                         sco = event.get_top_level_scope(ctf.scope.EVENT_FIELDS)
  71
  72                         # prev_comm
  73                         field = event.get_field(sco, "_prev_comm")
  74                         prev_comm = field.get_char_array()
  75                         if ctf.field_error():
  76                                 print("ERROR: Missing prev_comm context info")
  77
  78                         # prev_tid
  79                         field = event.get_field(sco, "_prev_tid")
  80                         prev_tid = field.get_int64()
  81                         if ctf.field_error():
  82                                 print("ERROR: Missing prev_tid context info")
  83
  84                         # prev_prio
  85                         field = event.get_field(sco, "_prev_prio")
  86                         prev_prio = field.get_int64()
  87                         if ctf.field_error():
  88                                 print("ERROR: Missing prev_prio context info")
  89
  90                         # prev_state
  91                         field = event.get_field(sco, "_prev_state")
  92                         prev_state = field.get_int64()
  93                         if ctf.field_error():
  94                                 print("ERROR: Missing prev_state context info")
  95
  96                         # next_comm
  97                         field = event.get_field(sco, "_next_comm")
  98                         next_comm = field.get_char_array()
  99                         if ctf.field_error():
 100                                 print("ERROR: Missing next_comm context info")
 101
 102                         # next_tid
 103                         field = event.get_field(sco, "_next_tid")
 104                         next_tid = field.get_int64()
 105                         if ctf.field_error():
 106                                 print("ERROR: Missing next_tid context info")
 107
 108                         # next_prio
 109                         field = event.get_field(sco, "_next_prio")
 110                         next_prio = field.get_int64()
 111                         if ctf.field_error():
 112                                 print("ERROR: Missing next_prio context info")
 113
 114                         # Output
 115                         print("sched_switch, pid = {}, TS = {}, prev_comm = {},\n\t"
 116                                 "prev_tid = {}, prev_prio = {}, prev_state = {},\n\t"
 117                                 "next_comm = {}, next_tid = {}, next_prio = {}".format(
 118                                 pid, event.get_timestamp(), prev_comm, prev_tid,
 119                                 prev_prio, prev_state, next_comm, next_tid, next_prio))
 120
 121                 break # Next event
 122
 123         # Next event
 124         ret = ctf_it.next()
 125         if ret < 0:
 126                 break
 127         event = ctf_it.read_event()
 128
 129 del ctf_it