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#! /usr/bin/env python
# SPDX-License-Identifier: GPL-2.0-only
"""Example to show how to enable a software event and track context switches."""
# -*- 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()
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