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