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()
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