From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: Where is the performance bottleneck? Date: Wed, 31 Aug 2005 09:26:45 +0200 Message-ID: <20050831072644.GF4018@suse.de> References: <20050829202529.GA32214@midnight.suse.cz> <20050831071126.GA7502@midnight.ucw.cz> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20050831071126.GA7502@midnight.ucw.cz> Sender: linux-raid-owner@vger.kernel.org To: Vojtech Pavlik Cc: Holger Kiehl , linux-raid , linux-kernel List-Id: linux-raid.ids On Wed, Aug 31 2005, Vojtech Pavlik wrote: > On Tue, Aug 30, 2005 at 08:06:21PM +0000, Holger Kiehl wrote: > > >>How does one determine the PCI-X bus speed? > > > > > >Usually only the card (in your case the Symbios SCSI controller) can > > >tell. If it does, it'll be most likely in 'dmesg'. > > > > > There is nothing in dmesg: > > > > Fusion MPT base driver 3.01.20 > > Copyright (c) 1999-2004 LSI Logic Corporation > > ACPI: PCI Interrupt 0000:02:04.0[A] -> GSI 24 (level, low) -> IRQ 217 > > mptbase: Initiating ioc0 bringup > > ioc0: 53C1030: Capabilities={Initiator,Target} > > ACPI: PCI Interrupt 0000:02:04.1[B] -> GSI 25 (level, low) -> IRQ 225 > > mptbase: Initiating ioc1 bringup > > ioc1: 53C1030: Capabilities={Initiator,Target} > > Fusion MPT SCSI Host driver 3.01.20 > > > > >To find where the bottleneck is, I'd suggest trying without the > > >filesystem at all, and just filling a large part of the block device > > >using the 'dd' command. > > > > > >Also, trying without the RAID, and just running 4 (and 8) concurrent > > >dd's to the separate drives could show whether it's the RAID that's > > >slowing things down. > > > > > Ok, I did run the following dd command in different combinations: > > > > dd if=/dev/zero of=/dev/sd?1 bs=4k count=5000000 > > I think a bs of 4k is way too small and will cause huge CPU overhead. > Can you try with something like 4M? Also, you can use /dev/full to avoid > the pre-zeroing. That was my initial thought as well, but since he's writing the io side should look correct. I doubt 8 dd's writing 4k chunks will gobble that much CPU as to make this much difference. Holger, we need vmstat 1 info while the dd's are running. A simple profile would be nice as well, boot with profile=2 and do a readprofile -r; run tests; readprofile > foo and send the first 50 lines of foo to this list. -- Jens Axboe