Date: Wed, 14 Sep 2005 22:20:13 +0200 From: Oliver Lehmann <lehmann@ans-netz.de> To: Scott Long <scottl@samsco.org> Cc: current@freebsd.org Subject: Re: low(er) disk performance with sched_4bsd then with sched_ule Message-ID: <20050914222013.178dc4dc.lehmann@ans-netz.de> In-Reply-To: <43286E37.40203@samsco.org> References: <20050914194612.15692485.lehmann@ans-netz.de> <43286E37.40203@samsco.org>
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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/
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