#! /usr/bin/python# -*- python -*-# -*- coding: utf-8 -*- import perf class tracepoint(perf.evsel):    def __init__(self, sys, name):        config = perf.tracepoint(sys, name)        perf.evsel.__init__(self,                            type   = perf.TYPE_TRACEPOINT,                            config = config,                            freq = 0, sample_period = 1, wakeup_events = 1,                            sample_type = perf.SAMPLE_PERIOD | perf.SAMPLE_TID | perf.SAMPLE_CPU | perf.SAMPLE_RAW | perf.SAMPLE_TIME) def main():    tp      = tracepoint("sched", "sched_switch")    cpus    = perf.cpu_map()    threads = perf.thread_map(-1)     evlist = perf.evlist(cpus, threads)    evlist.add(tp)    evlist.open()    evlist.mmap()     while True:        evlist.poll(timeout = -1)        for cpu in cpus:            event = evlist.read_on_cpu(cpu)            if not event:                continue             if not isinstance(event, perf.sample_event):                continue             print "time %u prev_comm=%s prev_pid=%d prev_prio=%d prev_state=0x%x ==> next_comm=%s next_pid=%d next_prio=%d" % (                   event.sample_time,                   event.prev_comm,                   event.prev_pid,                   event.prev_prio,                   event.prev_state,                   event.next_comm,                   event.next_pid,                   event.next_prio) if __name__ == '__main__':    main()