From mboxrd@z Thu Jan 1 00:00:00 1970 From: jmerkey Subject: Re: Where is the performance bottleneck? Date: Wed, 31 Aug 2005 09:59:39 -0600 Message-ID: <4315D3EB.4000601@utah-nac.org> References: <20050829202529.GA32214@midnight.suse.cz> <20050831071126.GA7502@midnight.ucw.cz> <20050831072644.GF4018@suse.de> <20050831120714.GT4018@suse.de> <20050831162053.GG4018@suse.de> <4315C9EB.2030506@utah-nac.org> <20050831171124.GH4018@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20050831171124.GH4018@suse.de> Sender: linux-raid-owner@vger.kernel.org To: Jens Axboe Cc: Holger Kiehl , Vojtech Pavlik , linux-raid , linux-kernel List-Id: linux-raid.ids 512 is not enough. It has to be larger. I just tried 512 and it still limits the data rates. Jeff Jens Axboe wrote: >On Wed, Aug 31 2005, jmerkey wrote: > > >>I have seen an 80GB/sec limitation in the kernel unless this value is >>changed in the SCSI I/O layer >>for 3Ware and other controllers during testing of 2.6.X series kernels. >> >>Change these values in include/linux/blkdev.h and performance goes from >>80MB/S to over 670MB/S on the 3Ware controller. >> >> >>//#define BLKDEV_MIN_RQ 4 >>//#define BLKDEV_MAX_RQ 128 /* Default maximum */ >>#define BLKDEV_MIN_RQ 4096 >>#define BLKDEV_MAX_RQ 8192 /* Default maximum */ >> >> > >That's insane, you just wasted 1MiB of preallocated requests on each >queue in the system! > >Please just do > ># echo 512 > /sys/block/dev/queue/nr_requests > >after boot for each device you want to increase the queue size too. 512 >should be enough with the 3ware. > > >