test/debug/seekbench.c

   1 /*
   2  * SEEKBENCH.C
   3  *
   4  * cc seekbench.c -o /tmp/sb
   5  *
   6  * This intentionally performs a sequence of seek/reads with ever
   7  * growing distances in a way that should be essentially uncached.
   8  * It attempts to defeat both OS caches and the HDs zone cache.
   9  *
  10  * The average read-latency per seek/read is calculated.
  11  *
  12  * This can heat up the hard drive so be careful.
  13  */
  14
  15 #include <sys/types.h>
  16 #include <sys/time.h>
  17 #include <stdio.h>
  18 #include <stdlib.h>
  19 #include <unistd.h>
  20 #include <stdarg.h>
  21 #include <fcntl.h>
  22 #include <libutil.h>
  23
  24 #define BLKSIZE         ((intmax_t)1024)
  25 #define BLKMASK         (BLKSIZE - 1)
  26
  27 char Buf[BLKSIZE];
  28
  29 int
  30 main(int ac, char **av)
  31 {
  32         struct timeval tv1;
  33         struct timeval tv2;
  34         off_t bytes;
  35         off_t base;
  36         off_t skip;
  37         intmax_t us;
  38         int fd;
  39         int count;
  40
  41         if (ac == 1) {
  42                 fprintf(stderr, "seekbench <blockdevice>\n");
  43                 exit(1);
  44         }
  45         fd = open(av[1], O_RDONLY);
  46         if (fd < 0) {
  47                 perror("open");
  48                 exit(1);
  49         }
  50         lseek(fd, 0L, 2);
  51         bytes = lseek(fd, 0L, 1);
  52         printf("%s: %jdMB\n", av[1], (intmax_t)bytes / 1024 / 1024);
  53         printf("distance avg-seek\n");
  54         skip = BLKSIZE;
  55         while (skip < bytes) {
  56                 count = 0;
  57                 gettimeofday(&tv1, NULL);
  58                 for (base = skip; base < bytes && count < 100; base += skip) {
  59                         lseek(fd, base, 0);
  60                         read(fd, Buf, BLKSIZE);
  61                         ++count;
  62                 }
  63                 gettimeofday(&tv2, NULL);
  64                 us = (tv2.tv_usec + 1000000 - tv1.tv_usec) +
  65                      (tv2.tv_sec - 1 - tv1.tv_sec) * 1000000;
  66                 if (skip < 100*1024*1024)
  67                         printf("%5jdKB %6.3fms\n",
  68                                 (intmax_t)skip / 1024,
  69                                 (double)us / 1000.0 / count);
  70                 else
  71                         printf("%5jdMB %6.3fms\n",
  72                                 (intmax_t)skip / 1024 / 1024,
  73                                 (double)us / 1000.0 / count);
  74                 skip += BLKSIZE;
  75                 if (skip < BLKSIZE * 25)
  76                         skip += BLKSIZE;
  77                 else
  78                         skip += (skip / 25 + BLKMASK) & ~BLKMASK;
  79         }
  80 }