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SubjectRe: very weired random io behavior
From
Date
sorry. my dumb.

here is not
x = (rand() >> 1) << 1;
but
x = (rand() >> 10) << 10;

file is in bytes while lba is in sector. ;P

ming



On Fri, 2005-08-26 at 16:08 -0400, Ming Zhang wrote:

> ---------------------------------------------------
> #define _LARGEFILE64_SOURCE
>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <sys/types.h>
> #include <sys/stat.h>
>
> int main(int argc, char *argv[])
> {
> int n;
> int i, count;
> char *name;
> char buf[4096];
> int fd;
>
> if (argc != 3) {
> printf("%s name count\n", argv[0]);
> exit(1);
> }
> name = argv[1];
> count = atoi(argv[2]);
>
> fd = open(name, O_CREAT|O_WRONLY, S_IRWXU);
> for (i = 0; i < count; i++) {
> unsigned long x;
>
> x = (rand() >> 1) << 1;
> lseek64(fd, x, SEEK_SET);
> write(fd, buf, 4096);
> }
> printf("done\n");
> close(fd);
> return 0;
> }
>

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