62 lines · python
1#! /usr/bin/env python2# SPDX-License-Identifier: GPL-2.0-only3# -*- python -*-4# -*- coding: utf-8 -*-5# twatch - Experimental use of the perf python interface6# Copyright (C) 2011 Arnaldo Carvalho de Melo <acme@redhat.com>7#8 9import perf10 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=123 (the default), makes perf reenable irq_vectors:local_timer_entry, when24 disabling nohz, not good for some use cases where all we want is to get25 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 continue38 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 replace46 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_OUT56 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