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Message-Id: <19970909231006.58788@mi.uni-koeln.de>
Date: Tue, 9 Sep 1997 23:10:06 +0200
From: Stefan Esser <se@FreeBSD.ORG>
To: Mats Lofkvist <mal@algonet.se>
Cc: current@FreeBSD.ORG
Subject: Re: lousy disk perf. under cpu load (was IDE vs SCSI)
References: <199709082256.AAA04008@kairos>
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On Sep 9, Mats Lofkvist <mal@algonet.se> wrote:
> I tested reading (and writing were possible) small blocks (4KB) on all
> my devices tonight. With iozone and bonnie I don't see anything really
> alarming except that the bonnie seek rate drops significantly when
> a "loader" is running (*). But dd from (and to) all my devices show the same
> results counting the number of transfers per second (= # pci interrupts / s):
> 
> 		rst0 r	rst0 w	sd0	rsd0	sd1	rsd1	cd0	rcd0
> unloaded	283	294	3700	2600	1134	1049	900	460
> loaded		23	22	50	26	24	23	25	22
> 
> rst0 is a sony sdt7000 dat tape on the ncr
> sd0 is a quantum viking w on the aic7880
> sd1 is a quantum capella on the ncr
> cd0 is a pioneer dr-u12x on the ncr

I definitely can't reproduce your numbers. There 
is something *very* wrong with your system!

> chip0 <Intel 82440FX (Natoma) PCI and memory controller> rev 2 on pci0:0
> fxp0 <Intel EtherExpress Pro 10/100B Ethernet> rev 1 int a irq 10 on pci0:6
> ahc0 <Adaptec aic7880 Ultra SCSI host adapter> rev 0 int a irq 10 on pci0:9
> vga0 <VGA-compatible display device> rev 0 int a irq 11 on pci0:11
> ncr0 <ncr 53c810a scsi> rev 18 int a irq 10 on pci0:17

Hmmm, you got all your PCI disk and LAN cards on
IRQ 10, which means there are three cards sharing
interrupts. The VGA is on IRQ 11, and it should
not really cause interrupts ...

Could you try to assign different IRQs to fxp0, ncr0 
and ahc0 ?

Shared interrupts should just work, and there should
not be a measurable impact on performance, but this
is the only thing that seems special in your system.

Regards, STefan