#! /usr/bin/env python# SPDX-License-Identifier: GPL-2.0-only# -*- python -*-# -*- coding: utf-8 -*-#   twatch - Experimental use of the perf python interface#   Copyright (C) 2011 Arnaldo Carvalho de Melo <acme@redhat.com># import perf def main(context_switch = 0, thread = -1):	cpus = perf.cpu_map()	threads = perf.thread_map(thread)	evsel = perf.evsel(type	  = perf.TYPE_SOFTWARE,			   config = perf.COUNT_SW_DUMMY,			   task = 1, comm = 1, mmap = 0, freq = 0,			   wakeup_events = 1, watermark = 1,			   sample_id_all = 1, context_switch = context_switch,			   sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU) 	"""What we want are just the PERF_RECORD_ lifetime events for threads,	 using the default, PERF_TYPE_HARDWARE + PERF_COUNT_HW_CYCLES & freq=1	 (the default), makes perf reenable irq_vectors:local_timer_entry, when	 disabling nohz, not good for some use cases where all we want is to get	 threads comes and goes... So use (perf.TYPE_SOFTWARE, perf_COUNT_SW_DUMMY,	 freq=0) instead.""" 	evsel.open(cpus = cpus, threads = threads);	evlist = perf.evlist(cpus, threads)	evlist.add(evsel)	evlist.mmap()	while True:		evlist.poll(timeout = -1)		for cpu in cpus:			event = evlist.read_on_cpu(cpu)			if not event:				continue			print("cpu: {0}, pid: {1}, tid: {2} {3}".format(event.sample_cpu,                                                                        event.sample_pid,                                                                        event.sample_tid,                                                                        event)) if __name__ == '__main__':    """	To test the PERF_RECORD_SWITCH record, pick a pid and replace	in the following line. 	Example output: cpu: 3, pid: 31463, tid: 31593 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31593, switch_out: 1 }cpu: 1, pid: 31463, tid: 31489 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31489, switch_out: 1 }cpu: 2, pid: 31463, tid: 31496 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31496, switch_out: 1 }cpu: 3, pid: 31463, tid: 31491 { type: context_switch, next_prev_pid: 31463, next_prev_tid: 31491, switch_out: 0 } 	It is possible as well to use event.misc & perf.PERF_RECORD_MISC_SWITCH_OUT	to figure out if this is a context switch in or out of the monitored threads. 	If bored, please add command line option parsing support for these options :-)    """    # main(context_switch = 1, thread = 31463)    main()