src/tests/system/benchmarks/forkbench.c

   1 /*
   2  * from ftp://ftp.netbsd.org/pub/NetBSD/misc/gmcgarry/bench/forkbench.tar.gz
   3  */
   4
   5 /* From 4.4 BSD sys/tests/benchmarks/forks.c. */
   6
   7 #include <unistd.h>
   8 #include <stdlib.h>
   9 #include <stdio.h>
  10 #include <sys/time.h>
  11 #include <sys/wait.h>
  12
  13 /*
  14  * Benchmark program to calculate fork+wait
  15  * overhead (approximately).  Process
  16  * forks and exits while parent waits.
  17  * The time to run this program is used
  18  * in calculating exec overhead.
  19  */
  20
  21 int
  22 main(argc, argv)
  23         char *argv[];
  24 {
  25         int nforks, i;
  26         char *cp;
  27         int pid, child, status, brksize;
  28         struct timeval before, after;
  29         unsigned elapsed;
  30
  31         if (argc < 3) {
  32                 printf("usage: %s number-of-forks sbrk-size\n", argv[0]);
  33                 exit(1);
  34         }
  35         nforks = atoi(argv[1]);
  36         if (nforks < 0) {
  37                 printf("%s: bad number of forks\n", argv[1]);
  38                 exit(2);
  39         }
  40         brksize = atoi(argv[2]);
  41         if (brksize < 0) {
  42                 printf("%s: bad size to sbrk\n", argv[2]);
  43                 exit(3);
  44         }
  45
  46         gettimeofday(&before, NULL);
  47         cp = (char *)sbrk(brksize);
  48         if (cp == (void *)-1) {
  49                 perror("sbrk");
  50                 exit(4);
  51         }
  52         for (i = 0; i < brksize; i += 1024)
  53                 cp[i] = i;
  54         for (i=0; i<nforks; i++) {
  55                 child = fork();
  56                 if (child == -1) {
  57                         perror("fork");
  58                         exit(-1);
  59                 }
  60                 if (child == 0)
  61                         _exit(-1);
  62                 while ((pid = wait(&status)) != -1 && pid != child)
  63                         ;
  64         }
  65         gettimeofday(&after, NULL);
  66         elapsed = 1000000 * (after.tv_sec - before.tv_sec);
  67         elapsed += (after.tv_usec - before.tv_usec);
  68         printf ("Time: %d microseconds.\n", elapsed/nforks);
  69         exit(0);
  70 }