Re: [git patches] IDE update

[Jens Axboe <axboe@suse.de>]

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

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