timeloop.c

   1 #include <errno.h>
   2 #include <stdlib.h>
   3 #include <unistd.h>
   4 #include <stdio.h>
   5 #include <sys/resource.h>
   6 #include <sys/time.h>
   7
   8 #include <glib.h>
   9
  10 static int n_children = 3;
  11 static int n_active_children;
  12 static int n_iters = 10000;
  13 static GMainLoop *loop;
  14
  15 void
  16 io_pipe (GIOChannel **channels)
  17 {
  18   int fds[2];
  19
  20   if (pipe(fds) < 0)
  21     {
  22       fprintf (stderr, "Cannot create pipe %s\n", g_strerror (errno));
  23       exit (1);
  24     }
  25
  26   channels[0] = g_io_channel_unix_new (fds[0]);
  27   channels[1] = g_io_channel_unix_new (fds[1]);
  28 }
  29
  30 gboolean
  31 read_all (GIOChannel *channel, char *buf, int len)
  32 {
  33   int bytes_read = 0;
  34   int count;
  35   GIOError err;
  36
  37   while (bytes_read < len)
  38     {
  39       err = g_io_channel_read (channel, buf + bytes_read, len - bytes_read, &count);
  40       if (err)
  41         {
  42           if (err != G_IO_ERROR_AGAIN)
  43             return FALSE;
  44         }
  45       else if (count == 0)
  46         return FALSE;
  47
  48       bytes_read += count;
  49     }
  50
  51   return TRUE;
  52 }
  53
  54 gboolean
  55 write_all (GIOChannel *channel, char *buf, int len)
  56 {
  57   int bytes_written = 0;
  58   int count;
  59   GIOError err;
  60
  61   while (bytes_written < len)
  62     {
  63       err = g_io_channel_write (channel, buf + bytes_written, len - bytes_written, &count);
  64       if (err && err != G_IO_ERROR_AGAIN)
  65         return FALSE;
  66
  67       bytes_written += count;
  68     }
  69
  70   return TRUE;
  71 }
  72
  73 void
  74 run_child (GIOChannel *in_channel, GIOChannel *out_channel)
  75 {
  76   int i;
  77   int val = 1;
  78   GTimer *timer = g_timer_new();
  79
  80   for (i = 0; i < n_iters; i++)
  81     {
  82       write_all (out_channel, (char *)&val, sizeof (val));
  83       read_all (in_channel, (char *)&val, sizeof (val));
  84     }
  85
  86   val = 0;
  87   write_all (out_channel, (char *)&val, sizeof (val));
  88
  89   val = g_timer_elapsed (timer, NULL) * 1000;
  90
  91   write_all (out_channel, (char *)&val, sizeof (val));
  92   g_timer_destroy (timer);
  93
  94   exit (0);
  95 }
  96
  97 gboolean
  98 input_callback (GIOChannel   *source,
  99                 GIOCondition  condition,
 100                 gpointer      data)
 101 {
 102   int val;
 103   GIOChannel *dest = (GIOChannel *)data;
 104
 105   if (!read_all (source, (char *)&val, sizeof(val)))
 106     {
 107       fprintf (stderr, "Unexpected EOF\n");
 108       exit (1);
 109     }
 110
 111   if (val)
 112     {
 113       write_all (dest, (char *)&val, sizeof(val));
 114
 115       return TRUE;
 116     }
 117   else
 118     {
 119       g_io_channel_close (source);
 120       g_io_channel_close (dest);
 121
 122       g_io_channel_unref (source);
 123       g_io_channel_unref (dest);
 124
 125       n_active_children--;
 126       if (n_active_children == 0)
 127         g_main_quit (loop);
 128
 129       return FALSE;
 130     }
 131 }
 132
 133 void
 134 create_child ()
 135 {
 136   int pid;
 137   GIOChannel *in_channels[2];
 138   GIOChannel *out_channels[2];
 139
 140   io_pipe (in_channels);
 141   io_pipe (out_channels);
 142
 143   pid = fork ();
 144
 145   if (pid > 0)                  /* Parent */
 146     {
 147       g_io_channel_close (in_channels[0]);
 148       g_io_channel_close (out_channels[1]);
 149
 150       g_io_add_watch (out_channels[0], G_IO_IN | G_IO_HUP,
 151                       input_callback, in_channels[1]);
 152     }
 153   else if (pid == 0)            /* Child */
 154     {
 155       g_io_channel_close (in_channels[1]);
 156       g_io_channel_close (out_channels[0]);
 157
 158       setsid ();
 159
 160       run_child (in_channels[0], out_channels[1]);
 161     }
 162   else                          /* Error */
 163     {
 164       fprintf (stderr, "Cannot fork: %s\n", g_strerror (errno));
 165       exit (1);
 166     }
 167 }
 168
 169 static double
 170 difftimeval (struct timeval *old, struct timeval *new)
 171 {
 172   return
 173     (new->tv_sec - old->tv_sec) * 1000. + (new->tv_usec - old->tv_usec) / 1000;
 174 }
 175
 176 int
 177 main (int argc, char **argv)
 178 {
 179   int i;
 180   struct rusage old_usage;
 181   struct rusage new_usage;
 182
 183   if (argc > 1)
 184     n_children = atoi(argv[1]);
 185
 186   if (argc > 2)
 187     n_iters = atoi(argv[2]);
 188
 189   printf ("Children: %d     Iters: %d\n", n_children, n_iters);
 190
 191   n_active_children = n_children;
 192   for (i = 0; i < n_children; i++)
 193     create_child ();
 194
 195   getrusage (RUSAGE_SELF, &old_usage);
 196   loop = g_main_new (FALSE);
 197   g_main_run (loop);
 198   getrusage (RUSAGE_SELF, &new_usage);
 199
 200   printf ("Elapsed user: %g\n",
 201           difftimeval (&old_usage.ru_utime, &new_usage.ru_utime));
 202   printf ("Elapsed system: %g\n",
 203           difftimeval (&old_usage.ru_stime, &new_usage.ru_stime));
 204   printf ("Elapsed total: %g\n",
 205           difftimeval (&old_usage.ru_utime, &new_usage.ru_utime) +
 206           difftimeval (&old_usage.ru_stime, &new_usage.ru_stime));
 207   printf ("total / iteration: %g\n",
 208           (difftimeval (&old_usage.ru_utime, &new_usage.ru_utime) +
 209            difftimeval (&old_usage.ru_stime, &new_usage.ru_stime)) /
 210           (n_iters * n_children));
 211
 212   return 0;
 213 }