Simple utility to measure disk random access time

[Linux Portal]

And a few graphs here: http://linux.inet.hr/how_fast_is_your_disk.html

Comments welcome!

#define _LARGEFILE64_SOURCE

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <time.h>
#include <signal.h>
#include <sys/fcntl.h>
#include <sys/ioctl.h>
#include <linux/fs.h>

#define BLOCKSIZE 512
#define TIMEOUT 30

int count;
time_t start;

void done()
{
        time_t end;

        time(&end);

        if (end < start + TIMEOUT) {
                printf(".");
                alarm(1);
                return;
        }

        if (count) {
          printf(".\nResults: %d seeks/second, %.2f ms random access time\n",
                 count / TIMEOUT, 1000.0 * TIMEOUT / count);
        }
        exit(EXIT_SUCCESS);
}

void handle(const char *string, int error)
{
        if (error) {
                perror(string);
                exit(EXIT_FAILURE);
        }
}

int main(int argc, char **argv)
{
        char buffer[BLOCKSIZE];
        int fd, retval;
        unsigned long numblocks;
        off64_t offset;

        setvbuf(stdout, NULL, _IONBF, 0);

        printf("Seeker v2.0, 2007-01-15, "
               "http://linux.inet.hr/how_fast_is_your_disk.html\n";);

        if (argc != 2) {
                printf("Usage: seeker <raw disk device>\n");
                exit(EXIT_SUCCESS);
        }

        fd = open(argv[1], O_RDONLY);
        handle("open", fd < 0);

        retval = ioctl(fd, BLKGETSIZE, &numblocks);
        handle("ioctl", retval == -1);
        printf("Benchmarking %s [%luMB], wait %d seconds",
               argv[1], numblocks / 2048, TIMEOUT);

        time(&start);
        srand(start);
        signal(SIGALRM, &done);
        alarm(1);

        for (;;) {
                offset = (off64_t) numblocks * random() / RAND_MAX;
                retval = lseek64(fd, BLOCKSIZE * offset, SEEK_SET);
                handle("lseek64", retval == (off64_t) -1);
                retval = read(fd, buffer, BLOCKSIZE);
                handle("read", retval < 0);
                count++;
        }
        /* notreached */
}
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