forkbench.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <libgen.h>
#include <sys/time.h>

#define IBUFSIZE	30

static void
usage(const char *prog)
{
	fprintf(stderr, "Usage: %s <number>\n", prog);
	exit(EXIT_FAILURE);
}

int
main(int argc, char **argv)
{
	char *prog;
	char *argbuf[5];
	char sec[IBUFSIZE], usec[IBUFSIZE], iter[IBUFSIZE];
	int n, rv, status;
	struct timeval start, now;

	if (argc < 1) {
		fprintf(stderr, "argc = %d\n", argc);
		return EXIT_FAILURE;
	}
	prog = basename(argv[0]);
	if (argc != 2 && argc != 4)
		usage(prog);

	n = atoi(argv[1]);
	if (n <= 0) {
		if (argc == 2)
			printf("nop\n");
		else {
			gettimeofday(&now, NULL);
			printf("%g\n",
			    now.tv_sec + now.tv_usec / 1000000.0 -
			    (atoi(argv[2]) + atoi(argv[3]) / 1000000.0));
		}
		return EXIT_SUCCESS;
	}

	if (strcmp(prog, "forkbench") == 0 ||
	    strcmp(prog, "vforkbench") == 0 ||
	    strcmp(prog, "forkrepeatbench") == 0 ||
	    strcmp(prog, "vforkrepeatbench") == 0 ||
	    strcmp(prog, "forkwaitrepeatbench") == 0 ||
	    strcmp(prog, "vforkwaitrepeatbench") == 0) {
		int test_vfork = 
		    strcmp(prog, "vforkbench") == 0 ||
		    strcmp(prog, "vforkrepeatbench") == 0 ||
		    strcmp(prog, "vforkwaitrepeatbench") == 0;
		int test_forkrepeat =
		    strcmp(prog, "forkrepeatbench") == 0 ||
		    strcmp(prog, "vforkrepeatbench") == 0 ||
		    strcmp(prog, "forkwaitrepeatbench") == 0 ||
		    strcmp(prog, "vforkwaitrepeatbench") == 0;
		int test_wait = 
		    strcmp(prog, "forkwaitrepeatbench") == 0 ||
		    strcmp(prog, "vforkwaitrepeatbench") == 0;

		gettimeofday(&start, NULL);
		while (--n >= 0) {
			if (test_vfork) {
				rv = vfork();
			} else {
				rv = fork();
			}
			if (rv == -1) {
				perror(test_vfork ? "vfork" : "fork");
				_exit(EXIT_FAILURE);
			}
			if (test_forkrepeat) {
				if (rv == 0) 
					_exit(EXIT_SUCCESS);
				if (test_wait) {
					rv = waitpid(rv, &status, 0);
					if (rv == -1)
						perror("waitpid");
				}
					
			} else {
				if (rv != 0) 
					_exit(EXIT_SUCCESS);
			}
		}
		gettimeofday(&now, NULL);
		printf("%g\n",
		       now.tv_sec + now.tv_usec / 1000000.0 -
		       (start.tv_sec + start.tv_usec / 1000000.0));
		_exit(EXIT_SUCCESS);
	}

	snprintf(iter, sizeof iter, "%d", n - 1);
	if (argc == 2) {
		gettimeofday(&now, NULL);
		snprintf(sec, sizeof sec, "%ld", (long)now.tv_sec);
		snprintf(usec, sizeof usec, "%ld", (long)now.tv_usec);
		argbuf[0] = argv[0];
		argbuf[1] = iter;
		argbuf[2] = sec;
		argbuf[3] = usec;
		argbuf[4] = NULL;
	} else {
		argbuf[0] = argv[0];
		argbuf[1] = iter;
		argbuf[2] = argv[2];
		argbuf[3] = argv[3];
		argbuf[4] = NULL;
	}

	if (strcmp(prog, "forkexecbench") == 0 ||
	    strcmp(prog, "vforkexecbench") == 0) {
		int test_vfork = strcmp(prog, "vforkexecbench") == 0;

		if (test_vfork) {
			rv = vfork();
		} else {
			rv = fork();
		}
		if (rv == -1) {
			perror(test_vfork ? "vfork" : "fork");
		} else if (rv != 0) {
			_exit(EXIT_SUCCESS);
		}
		execv(prog, argbuf);
		perror("execv");
		_exit(EXIT_FAILURE);
	} else if(strcmp(prog, "execbench") == 0) {
		execv(prog, argbuf);
		perror("execv");
		return EXIT_FAILURE;
	} else {
		fprintf(stderr, "unknown program name: %s\n", prog);
	}
	/*NOTREACHED*/
	return EXIT_FAILURE;
}