On Mon, 21 Feb 2005 12:00:48 -0800 (PST), Linus Torvalds <[EMAIL PROTECTED]> wrote:
> That said, I'm surprised that the difference in performance is _that_ > large. Regardless of whether the disk blocksize is 512 bytes or 4096 > bytes, you should be getting IO merging - it might use more CPU time, but > the actual IO should still be done in much larger blocks. I am surprised too. Jens says "ub effectively disables merging by setting max hw/phys segment limit of 1." But surely this ought not to be a problem for reads within the same page. > int size = 4096; > ioctl(fd, BLKBSZSET, &size); Thank you for the tip. This works fine, 4KB I/O is restored for dd. However, I still have this problem with people who use ub to read CF sticks from their cameras, mounted as FAT or VFAT. I verified that the effect of this ioctl disappears at mount time, just as you said. I'll think what I can do about it. -- Pete - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
