2007-01-16 14:49:47

by Linux Portal

Subject: Simple utility to measure disk random access time

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 */
}

2007-01-16 18:59:12

by Bill Davidsen

Subject: Re: Simple utility to measure disk random access time

Linux Portal wrote:
> And a few graphs here: http://linux.inet.hr/how_fast_is_your_disk.html
>
> Comments welcome!

These results:

gaimboi:davidsen> ./da /dev/hdb
Seeker v2.0, 2007-01-15, http://linux.inet.hr/how_fast_is_your_disk.html
Benchmarking /dev/hdb [0MB], wait 30 seconds..............................
Results: 565841 seeks/second, 0.00 ms random access time
gaimboi:davidsen> ./da /dev/hda
Seeker v2.0, 2007-01-15, http://linux.inet.hr/how_fast_is_your_disk.html
Benchmarking /dev/hda [19092MB], wait 30
seconds..............................
Results: 49 seeks/second, 20.20 ms random access time
gaimboi:davidsen> ./da /dev/hdc
Seeker v2.0, 2007-01-15, http://linux.inet.hr/how_fast_is_your_disk.html
Benchmarking /dev/hdc [57241MB], wait 30
seconds..............................
Results: 64 seeks/second, 15.56 ms random access time


led to this patch:

RCS file: RCS/disk_access.c,v
retrieving revision 1.1
diff -r1.1 disk_access.c
67a68,72
> if (numblocks <= 0) {
> /* pretty small disk found here */
> printf("Disk too small, size: %d blocks\n", numblocks);
> exit(EXIT_FAILURE);
> }
69a75
>

and this warning:

gaimboi:davidsen> ./da /dev/hdb
Seeker v2.0, 2007-01-15, http://linux.inet.hr/how_fast_is_your_disk.html
Disk too small, size: 0 blocks


--
bill davidsen <[email protected]>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979