RE: Where is the performance bottleneck?

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:

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The U320 SCSI controller has a 64 bit PCI-X bus for itself, there is no

other

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device on that bus. Unfortunatly I was unable to determine at what

speed

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it is running, here the output from lspci -vv:

...

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                 Status: Bus=2 Dev=4 Func=0 64bit+ 133MHz+ SCD- USC-,

DC=simple,

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the "133MHz+" is a good sign.  OTOH the latency (72) seems rather low -

my

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understanding is that that would noticably limit the size of burst

transfers.

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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?

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Version  1.03        ------Sequential Output------ --Sequential Input-

--Random-

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                      -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--

--Seeks--

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Machine         Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP

/sec %CP

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Raid0 (8 disk)15744M 54406  96 247419 90 100752 25 60266  98 226651 29

830.2   1

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Raid0s(4 disk)15744M 54915  97 253642 89 73976  18 59445  97 198372 24

659.8   1

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Raid0s(4 disk)15744M 54866  97 268361 95 72852  17 59165  97 187183 22

666.3   1

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you're obviously saturating something already with 2 disks.  did you

play

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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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