/*
* self_pipe.c - dual process ping-pong example to stress PMU context switch of one process
*
* Copyright (c) 2008 Google, Inc
* Contributed by Stephane Eranian <eranian@gmail.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
* of the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
* INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
* HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
* CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
* OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* This file is part of libpfm, a performance monitoring support library for
* applications on Linux.
*/
#include <sys/types.h>
#include <inttypes.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdarg.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
#include <sched.h>
#include <err.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <perfmon/pfmlib_perf_event.h>
#include "perf_util.h"
static struct {
const char *events;
int cpu;
int delay;
} options;
int
pin_cpu(pid_t pid, unsigned int cpu)
{
cpu_set_t mask;
CPU_ZERO(&mask);
CPU_SET(cpu, &mask);
return sched_setaffinity(pid, sizeof(mask), &mask);
}
static volatile int quit;
void sig_handler(int n)
{
quit = 1;
}
static void
do_child(int fr, int fw)
{
char c;
ssize_t ret;
for(;;) {
ret = read(fr, &c, 1);
if (ret < 0)
break;
ret = write(fw, "c", 1);
if (ret < 0)
break;
}
printf("child exited\n");
exit(0);
}
static void
measure(void)
{
perf_event_desc_t *fds = NULL;
int num_fds = 0;
uint64_t values[3];
ssize_t n;
int i, ret;
int pr[2], pw[2];
pid_t pid;
char cc = '0';
ret = pfm_initialize();
if (ret != PFM_SUCCESS)
err(1, "cannot initialize libpfm");
if (options.cpu == -1) {
srandom(getpid());
options.cpu = random() % sysconf(_SC_NPROCESSORS_ONLN);
}
ret = pipe(pr);
if (ret)
err(1, "cannot create read pipe");
ret = pipe(pw);
if (ret)
err(1, "cannot create write pipe");
ret = perf_setup_list_events(options.events, &fds, &num_fds);
if (ret || !num_fds)
exit(1);
for(i=0; i < num_fds; i++) {
fds[i].hw.disabled = 1;
fds[i].hw.read_format = PERF_FORMAT_SCALE;
fds[i].fd = perf_event_open(&fds[i].hw, 0, -1, -1, 0);
if (fds[i].fd == -1)
err(1, "cannot open event %d", i);
}
/*
* Pin to CPU0, inherited by child process. That will enforce
* the ping-pionging and thus stress the PMU context switch
* which is what we want
*/
ret = pin_cpu(getpid(), options.cpu);
if (ret)
err(1, "cannot pin to CPU%d", options.cpu);
printf("Both processes pinned to CPU%d, running for %d seconds\n", options.cpu, options.delay);
/*
* create second process which is not monitoring at the moment
*/
switch(pid=fork()) {
case -1:
err(1, "cannot create child\n");
exit(1); /* not reached */
case 0:
/* do not inherit session fd */
for(i=0; i < num_fds; i++)
close(fds[i].fd);
/* pr[]: write master, read child */
/* pw[]: read master, write child */
close(pr[1]); close(pw[0]);
do_child(pr[0], pw[1]);
exit(1);
}
close(pr[0]);
close(pw[1]);
/*
* Let's roll now
*/
prctl(PR_TASK_PERF_EVENTS_ENABLE);
signal(SIGALRM, sig_handler);
alarm(options.delay);
/*
* ping pong loop
*/
while(!quit) {
n = write(pr[1], "c", 1);
if (n < 1)
err(1, "write failed");
n = read(pw[0], &cc, 1);
if (n < 1)
err(1, "read failed");
}
prctl(PR_TASK_PERF_EVENTS_DISABLE);
for(i=0; i < num_fds; i++) {
uint64_t val;
double ratio;
ret = read(fds[i].fd, values, sizeof(values));
if (ret == -1)
err(1,"pfm_read error");
if (ret != sizeof(values))
errx(1, "did not read correct amount %d", ret);
val = perf_scale(values);
ratio = perf_scale_ratio(values);
if (ratio == 1.0)
printf("%20"PRIu64" %s\n", val, fds[i].name);
else
if (ratio == 0.0)
printf("%20"PRIu64" %s (did not run: competing session)\n", val, fds[i].name);
else
printf("%20"PRIu64" %s (scaled from %.2f%% of time)\n", val, fds[i].name, ratio*100.0);
}
/*
* kill child process
*/
kill(SIGKILL, pid);
/*
* close pipes
*/
close(pr[1]);
close(pw[0]);
/*
* and destroy our session
*/
for(i=0; i < num_fds; i++)
close(fds[i].fd);
perf_free_fds(fds, num_fds);
/* free libpfm resources cleanly */
pfm_terminate();
}
static void
usage(void)
{
printf("usage: self_pipe [-h] [-c cpu] [-d delay] [-e event1,event2,...]\n");
}
int
main(int argc, char **argv)
{
int c;
options.cpu = -1;
options.delay = -1;
while ((c=getopt(argc, argv,"he:c:d:")) != -1) {
switch(c) {
case 'e':
options.events = optarg;
break;
case 'c':
options.cpu = atoi(optarg);
break;
case 'd':
options.delay = atoi(optarg);
break;
case 'h':
usage();
exit(0);
default:
errx(1, "unknown error");
}
}
if (!options.events)
options.events = "cycles,instructions";
if (options.delay == -1)
options.delay = 10;
measure();
return 0;
}