tools/perf/python/twatch.py

   1 #! /usr/bin/python
   2 # -*- python -*-
   3 # -*- coding: utf-8 -*-
   4 #   twatch - Experimental use of the perf python interface
   5 #   Copyright (C) 2011 Arnaldo Carvalho de Melo <acme@redhat.com>
   6 #
   7 #   This application is free software; you can redistribute it and/or
   8 #   modify it under the terms of the GNU General Public License
   9 #   as published by the Free Software Foundation; version 2.
  10 #
  11 #   This application is distributed in the hope that it will be useful,
  12 #   but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 #   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 #   General Public License for more details.
  15
  16 import perf
  17
  18 def main(context_switch = 0, thread = -1):
  19         cpus = perf.cpu_map()
  20         threads = perf.thread_map(thread)
  21         evsel = perf.evsel(type   = perf.TYPE_SOFTWARE,
  22                            config = perf.COUNT_SW_DUMMY,
  23                            task = 1, comm = 1, mmap = 0, freq = 0,
  24                            wakeup_events = 1, watermark = 1,
  25                            sample_id_all = 1, context_switch = context_switch,
  26                            sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU)
  27
  28         """What we want are just the PERF_RECORD_ lifetime events for threads,
  29          using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1
  30          (the default), makes perf reenable irq_vectors:local_timer_entry, when
  31          disabling nohz, not good for some use cases where all we want is to get
  32          threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,
  33          freq=0) instead."""
  34
  35         evsel.open(cpus = cpus, threads = threads);
  36         evlist = perf.evlist(cpus, threads)
  37         evlist.add(evsel)
  38         evlist.mmap()
  39         while True:
  40                 evlist.poll(timeout = -1)
  41                 for cpu in cpus:
  42                         event = evlist.read_on_cpu(cpu)
  43                         if not event:
  44                                 continue
  45                         print("cpu: {0}, pid: {1}, tid: {2} {3}".format(event.sample_cpu,
  46                                                                         event.sample_pid,
  47                                                                         event.sample_tid,
  48                                                                         event))
  49
  50 if __name__ == '__main__':
  51     """
  52         To test the PERF_RECORD_SWITCH record, pick a pid and replace
  53         in the following line.
  54
  55         Example output:
  56
  57 cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }
  58 cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }
  59 cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
  60 cpu: 3, pid: 31463, tid: 31491 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31491, switch_out: 0 }
  61
  62         It is possible as well to use event.misc & perf.PERF_RECORD_MISC_SWITCH_OUT
  63         to figure out if this is a context switch in or out of the monitored threads.
  64
  65         If bored, please add command line option parsing support for these options :-)
  66     """
  67     # main(context_switch = 1, thread = 31463)
  68     main()