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SubjectRE: Where is the performance bottleneck?
Date
In most of your results, your CPU usage is very high.  Once you get to about
90% usage, you really can't do much else, unless you can improve the CPU
usage.

Guy

> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
> owner@vger.kernel.org] On Behalf Of Holger Kiehl
> Sent: Tuesday, August 30, 2005 3:09 PM
> To: Mark Hahn
> Cc: linux-raid; linux-kernel
> Subject: Re: Where is the performance bottleneck?
>
> On Mon, 29 Aug 2005, Mark Hahn wrote:
>
> >> The U320 SCSI controller has a 64 bit PCI-X bus for itself, there is no
> other
> >> device on that bus. Unfortunatly I was unable to determine at what
> speed
> >> it is running, here the output from lspci -vv:
> > ...
> >> Status: Bus=2 Dev=4 Func=0 64bit+ 133MHz+ SCD- USC-,
> DC=simple,
> >
> > the "133MHz+" is a good sign. OTOH the latency (72) seems rather low -
> my
> > understanding is that that would noticably limit the size of burst
> transfers.
> >
> I have tried with 128 and 144, but the transfer rate is only a little
> bit higher barely measurable. Or what values should I try?
>
> >
> >> Version 1.03 ------Sequential Output------ --Sequential Input-
> --Random-
> >> -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
> --Seeks--
> >> Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP
> /sec %CP
> >> Raid0 (8 disk)15744M 54406 96 247419 90 100752 25 60266 98 226651 29
> 830.2 1
> >> Raid0s(4 disk)15744M 54915 97 253642 89 73976 18 59445 97 198372 24
> 659.8 1
> >> Raid0s(4 disk)15744M 54866 97 268361 95 72852 17 59165 97 187183 22
> 666.3 1
> >
> > you're obviously saturating something already with 2 disks. did you
> play
> > with "blockdev --setra" setings?
> >
> Yes, I did play a little bit with it but this only changed read
> performance,
> it made no measurable difference when writting.
>
> Thanks,
> Holger
>
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