/*

 * 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;

}