Re: 40% IDE performance regression going from FC3 to FC5 with same kernel

["Alessandro Suardi" <alessandro.suardi@gmail.com>]

On 4/11/06, Alessandro Suardi <alessandro.suardi@gmail.com> wrote:
> 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.
>

Filed bugzilla #188630.

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=188630

Thanks,

--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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