Re: [git patches] IDE update

Bartlomiej Zolnierkiewicz
2005-07-04T20:48:05Z

On 7/4/05, Al Boldi <a1426z@gawab.com> 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
> > >>
> > >>It feels like DMA is not being applied properly in 2.6.12.
> > >
> > > Same on 2.6.10,11,12.
> > > No errors though, only sluggish system.
>
> What about earlier kernels?
> Please try to narrow down the problem to a specific kernel version.
> }
>
> Don't know about 2.6.0-2.6.9, but 2.4.31 is ok.

2.4 -> 2.6 means zillions of changes.

> Bartlomiej,
> When you compare 2.4.31 with 2.6.12 don't you see this problem on your
> machine?

Unfortunately I've never encountered this problem on any machine.

> If you have a fast system the slowdown won't show, but your IOWAIT will be
> higher anyway!

AFAIK high iowait is a known block layer problem

> It feels like running on PIO instead of DMA.