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SubjectRe: 40% IDE performance regression going from FC3 to FC5 with same kernel
On 4/11/06, Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
> >> > I'll be filing a FC5 performance bug for this but would like an opinion
> >> > from the IDE kernel people just in case this has already been seen...
> >> >
> >> > I just upgraded my home K7-800, 512MB RAM box from FC3 to FC5
> >> > and noticed a disk performance slowdown while copying files around.
> >>
> >> Just another suggestion: try eliminating/pinpointing I/O scheduler issues
> >> (switch e.g. to "noop" at /sys/block/hda/queue/scheduler and compare again)
> >
> >Thanks Andi. Tried every scheduler (my default is anticipatory) and
> > there aren't meaningful differences - 18.3 to 18.6MB/s.
> >
> >As a further data point, my box can burn a 8x DVD+R at up to 7.1x
> > average speed under FC3, while it barely keeps up with 4x in FC5.
>
> Since you said it happens with the same kernel, I think it's caused by
> userspace (do the boot-with-"-b" thing and you'll know). Possible someone
> setting DMA to speeds as low as udma4 or udma2.

Booting into /sbin/init -b indeed shows I get 33.3MB/s from hdparm,
as in FC3. DMA is (again according to hdparm) udma4 both booted
normally and in emergency mode. Note that at this point I'm testing
2.6.17-rc1-git4 in FC5, not to be trailing current kernels too much
(and yes, I already tested that normal 2.6.17-rc1-git4 boot in FC5
gets 18.5MB/s - without IDE_GENERIC, so that is also clearly a
non relevant factor).

As per Bill Davidsen's question in another email, blockdev --getra
shows 256, which is the same value that hdparm shows.

--alessandro

"Dreamer ? Each one of us is a dreamer. We just push it down deep because
we are repeatedly told that we are not allowed to dream in real life"
(Reinhold Ziegler)
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