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
9import perf
10
11def 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
43if __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
50cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }
51cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }
52cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }
53cpu: 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()
62