fork vs vfork

fork-vs-vfork.c

/*
 * Copyright (c) 2011, Ben Noordhuis <[email protected]>
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE /* pipe2 */
#endif

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>

#include <unistd.h>
#include <signal.h>
#include <fcntl.h>

#include <sys/types.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/wait.h>

#ifdef __linux__
#include <linux/version.h>
/* pipe2() requires linux >= 2.6.27 and glibc >= 2.9 */
#define HAVE_PIPE2 \
  defined(LINUX_VERSION_CODE) && defined(__GLIBC_PREREQ) && LINUX_VERSION_CODE >= 0x2061B && __GLIBC_PREREQ(2, 9))
#endif

#define assert_errno()          \
  do {                          \
    if (errno != 0) {           \
      fprintf(stderr,           \
              "%s:%d: %s\n",    \
              __FILE__,         \
              __LINE__,         \
              strerror(errno)); \
      abort();                  \
    }                           \
  }                             \
  while (0);

#define E(expr) (expr); assert_errno();


int main(int argc, char **argv) {
  int status;
  pid_t pid;
  int i;

  (void) argc;

  if (argv[1])
    return 42;

  for (i = 0; i < 10e3; i++) {
#ifdef VFORK
    E(pid = vfork());
#else
    E(pid = fork());
#endif

    if (pid) {
      E(waitpid(pid, &status, 0));
      assert(WIFEXITED(status));
      assert(WEXITSTATUS(status) == 42);
    }
    else {
      char *argp[] = { argv[0], ".", NULL };
      char *envp[] = { NULL };
      execve(argv[0], argp, envp);
      _exit(127);
    }
  }

  return 0;
}

fork.stats

$ time ./fork
real    0m6.694s
user    0m0.000s
sys     0m0.760s

$ time ./fork
real    0m6.834s
user    0m0.030s
sys     0m0.750s

$ time ./fork
real    0m6.872s
user    0m0.050s
sys     0m0.750s

vfork.stats

$ time ./fork
real    0m5.006s
user    0m0.000s
sys     0m0.300s

$ time ./fork
real    0m5.590s
user    0m0.000s
sys     0m0.330s

$ time ./fork
real    0m5.332s
user    0m0.020s
sys     0m0.290s