unix4lyfe git - diskpinger/blob - diskpinger.c

   1 /* emikulic@gmail.com was here 2013 */
   2 #define  _GNU_SOURCE  /* for O_NOATIME and O_DIRECT */
   3
   4 #include <sys/types.h>
   5 #include <sys/stat.h>
   6 #include <err.h>
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include <stdio.h>
  10 #include <unistd.h>
  11 #include <stdlib.h>
  12 #include <time.h>
  13
  14 static const char scratch_file_name[] = "scratch";
  15 /* also block and fragment size of root fs: */
  16 static const size_t buf_size = 4096;
  17 /* write at most this often: */
  18 static const int period_usec = 500000;
  19
  20 int main() {
  21   int fd;
  22   char *buf;
  23
  24   if (posix_memalign((void**)(&buf), buf_size, buf_size) != 0)
  25     errx(1, "posix_memalign() failed");
  26
  27   if ((fd = open(scratch_file_name,
  28                  O_CREAT | O_TRUNC | O_NOATIME | O_RDWR | O_DIRECT,
  29                  0600)) == -1)
  30     err(1, "open() failed");
  31   /* O_SYNC doesn't seem to be needed here. */
  32
  33   for (;;) {
  34     ssize_t ret;
  35     struct timespec t1, t2, tr;
  36     int diff_sec, diff_nsec, sleep_len;
  37
  38     if (clock_gettime(CLOCK_REALTIME, &tr) == -1)
  39       err(1, "clock_gettime() failed");
  40     if (clock_gettime(CLOCK_MONOTONIC, &t1) == -1)
  41       err(1, "clock_gettime() failed");
  42
  43     ret = pwrite(fd, buf, buf_size, 0);
  44     if (ret == -1)
  45       err(1, "pwrite() failed (errno=%d)", errno);
  46     if (ret != buf_size)
  47       warn("pwrite() returned %d, expected %d", (int)ret, (int)buf_size);
  48
  49     if (clock_gettime(CLOCK_MONOTONIC, &t2) == -1)
  50       err(1, "clock_gettime() failed");
  51
  52     diff_sec = t2.tv_sec - t1.tv_sec;
  53     diff_nsec = t2.tv_nsec - t1.tv_nsec;
  54     if (diff_nsec < 0) {
  55       diff_sec--;
  56       diff_nsec += 1000000000;
  57     }
  58
  59     printf("r %d.%09d m %d.%09d wr %d.%09d\n",
  60            (int)tr.tv_sec, (int)tr.tv_nsec,
  61            (int)t1.tv_sec, (int)t1.tv_nsec,
  62            diff_sec, diff_nsec);
  63     fflush(stdout);
  64
  65     if (diff_sec > 0) {
  66       sleep_len = 1;
  67     } else {
  68       sleep_len = period_usec - diff_nsec / 1000;
  69       if (sleep_len < 0)
  70         sleep_len = 1;
  71     }
  72     usleep(sleep_len);
  73   }
  74   return 0;
  75 }
  76 /* vim:set ts=2 sw=2 et tw=80: */