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On Thu, Jan 10, 2002 at 01:05:51AM -0600, Richard Rauch wrote:
> > > I dropped in the ZA snapshot.  It does not help at all with the disk.
> 
> Okay, amendment: I was using dd raw-read performance, which still takes up
> to 30 seconds to read 10 blocks of 1 MB each.  I tried varying the
> block-sizes, though, and got some more interesting results:
> 
> For 10MB of data, 1MB at a time, 30 to 45 seconds.
>                   512bytes        8
>                   1K             14
>                   2K             14
>                   4K             15
>                   8K             15
>                   16K            15

Can you try the attached program ?
usage: /usr/bin/time ./tst /dev/rwd0d 1000

This measures the bandwidth between the disk cache and the host.

-- 
Manuel Bouyer <bouyer@antioche.eu.org>
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#include <fcntl.h>
#include <unistd.h>

main(int argc, char **argv)
{
	static char buf[64*1024];
	int fd, i;

	fd = open(argv[1], O_RDONLY, 0);
	if (fd < 0) {
		perror("open");
		exit(1);
	}
	for (i = 0; i < atoi(argv[2]); i++) {
		if (read(fd, buf, sizeof(buf)) != sizeof(buf)) {
			perror("read");
			exit(1);
		}
		if (lseek(fd, 0, SEEK_SET) < 0) {
			perror("seek");
			exit(1);
		}
			
	}
	exit(0);
}

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