low(er) disk performance with sched_4bsd then with sched_ule

[Kris Kennaway]

On Wed, Sep 14, 2005 at 10:20:13PM +0200, Oliver Lehmann wrote:
> Scott Long wrote:
> 
> > Oliver Lehmann wrote:
> > 
> > > Any idea where the 30MB/sec drawback comes from and if I missed sth.?
> > > I mean why there are 30MB/s more or less is worth to think about imho.
> > > 
> > 
> > Indeed.  This definitely warrants much more testing and investigation. 
> > My best guess is that ULE is allowing the uio copies of the data between
> > kernel and userland to complete with fewer interruptions.  It could also
> > be better about keeping the threads from ping-ponging between CPUs.  Can
> > you retest with different block sizes, ranging from 4k to 1m?
> 
> http://pofo.de/tmp/dd_ULE.txt
> http://pofo.de/tmp/dd_4BSD.txt
> 
> btw. the RAID strip size is 64k

Using schedgraph should be helpful to investigate why the two
schedulers differ so much.

Kris
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