RE: Where is the performance bottleneck?

["Guy" <bugzilla@watkins-home.com>]

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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