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Date: Wed, 14 Sep 2005 22:20:13 +0200
From: Oliver Lehmann <lehmann@ans-netz.de>
To: Scott Long <scottl@samsco.org>
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Subject: Re: low(er) disk performance with sched_4bsd then with sched_ule
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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


-- 
 Oliver Lehmann
  http://www.pofo.de/
  http://wishlist.ans-netz.de/