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
main(int ac,char ** av)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 }
81