Re: [git patches] IDE update

Jens Axboe
2005-07-05T10:13:08Z

On Tue, Jul 05 2005, Ondrej Zary wrote:
> André Tomt wrote:
> >Al Boldi wrote:
> >
> >>Bartlomiej Zolnierkiewicz wrote: {
> >>
> >>>>>On 7/4/05, Al Boldi <a1426z@gawab.com> wrote:
> >>>>>Hdparm -tT gives 38mb/s in 2.4.31
> >>>>>Cat /dev/hda > /dev/null gives 2% user 33% sys 65% idle
> >>>>>
> >>>>>Hdparm -tT gives 28mb/s in 2.6.12
> >>>>>Cat /dev/hda > /dev/null gives 2% user 25% sys 0% idle 73% IOWAIT
> >
> >
> >The "hdparm doesn't get as high scores as in 2.4" is a old discussed to
> >death "problem" on LKML. So far nobody has been able to show it affects
> >anything but that pretty useless quasi-benchmark.
> >
>
> No, it's not a problem with hdparm. hdparm only shows that there is
> _really_ a problem:
>
> 2.6.12
> root@pentium:/home/rainbow# time dd if=/dev/hda of=/dev/null bs=512
> count=1048576
> 1048576+0 records in
> 1048576+0 records out
>
> real 0m32.339s
> user 0m1.500s
> sys 0m14.560s
>
> 2.4.26
> root@pentium:/home/rainbow# time dd if=/dev/hda of=/dev/null bs=512
> count=1048576
> 1048576+0 records in
> 1048576+0 records out
>
> real 0m23.858s
> user 0m1.750s
> sys 0m15.180s

Perhaps some read-ahead bug. What happens if you use bs=128k for
instance?

--
Jens Axboe