tools/perf/python/twatch.py

   1 #! /usr/bin/env python
   2 # SPDX-License-Identifier: GPL-2.0-only
   3 # -*- python -*-
   4 # -*- coding: utf-8 -*-
   5 #   twatch - Experimental use of the perf python interface
   6 #   Copyright (C) 2011 Arnaldo Carvalho de Melo <acme@redhat.com>
   7 #
   8
   9 import perf
  10
  11 def main(context_switch = 0, thread = -1):
  12         cpus = perf.cpu_map()
  13         threads = perf.thread_map(thread)
  14         evsel = perf.evsel(type   = perf.TYPE_SOFTWARE,
  15                            config = perf.COUNT_SW_DUMMY,
  16                            task = 1, comm = 1, mmap = 0, freq = 0,
  17                            wakeup_events = 1, watermark = 1,
  18                            sample_id_all = 1, context_switch = context_switch,
  19                            sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU)
  20
  21         """What we want are just the PERF_RECORD_ lifetime events for threads,
  22          using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1
  23          (the default), makes perf reenable irq_vectors:local_timer_entry, when
  24          disabling nohz, not good for some use cases where all we want is to get
  25          threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,
  26          freq=0) instead."""
  27
  28         evsel.open(cpus = cpus, threads = threads);
  29         evlist = perf.evlist(cpus, threads)
  30         evlist.add(evsel)
  31         evlist.mmap()
  32         while True:
  33                 evlist.poll(timeout = -1)
  34                 for cpu in cpus:
  35                         event = evlist.read_on_cpu(cpu)
  36                         if not event:
  37                                 continue
  38                         print("cpu: {0}, pid: {1}, tid: {2} {3}".format(event.sample_cpu,
  39                                                                         event.sample_pid,
  40                                                                         event.sample_tid,
  41                                                                         event))
  42
  43 if __name__ == '__main__':
  44     """
  45         To test the PERF_RECORD_SWITCH record, pick a pid and replace
  46         in the following line.
  47
  48         Example output:
  49
  50 cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }
  51 cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }
  52 cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
  53 cpu: 3, pid: 31463, tid: 31491 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31491, switch_out: 0 }
  54
  55         It is possible as well to use event.misc & perf.PERF_RECORD_MISC_SWITCH_OUT
  56         to figure out if this is a context switch in or out of the monitored threads.
  57
  58         If bored, please add command line option parsing support for these options :-)
  59     """
  60     # main(context_switch = 1, thread = 31463)
  61     main()