From owner-freebsd-hackers@FreeBSD.ORG Sun May 8 14:29:49 2005 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id A0A5416A4E4; Sun, 8 May 2005 14:29:49 +0000 (GMT) Received: from multiplay.co.uk (www1.multiplay.co.uk [212.42.16.7]) by mx1.FreeBSD.org (Postfix) with ESMTP id B7BCA43D6D; Sun, 8 May 2005 14:29:48 +0000 (GMT) (envelope-from killing@multiplay.co.uk) Received: from vader ([212.135.219.179]) by multiplay.co.uk (multiplay.co.uk [212.42.16.7]) (MDaemon.PRO.v8.0.2.R) with ESMTP id md50001392399.msg; Sun, 08 May 2005 15:25:43 +0100 Message-ID: <001c01c553da$5554e490$b3db87d4@multiplay.co.uk> From: "Steven Hartland" To: "Scott Long" References: <069901c54bfd$2967ba40$7f06000a@int.mediasurface.com><427D5AA0.1080609@withagen.nl><002b01c553be$93a5b790$b3db87d4@multiplay.co.uk> <427E0F77.50006@samsco.org> Date: Sun, 8 May 2005 15:29:21 +0100 MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="iso-8859-1"; reply-type=response Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2900.2527 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2527 X-Spam-Processed: multiplay.co.uk, Sun, 08 May 2005 15:25:43 +0100 (not processed: message from valid local sender) X-MDRemoteIP: 212.135.219.179 X-Return-Path: killing@multiplay.co.uk X-MDAV-Processed: multiplay.co.uk, Sun, 08 May 2005 15:25:46 +0100 cc: freebsd-hackers@freebsd.org cc: freebsd-current@freebsd.org cc: Willem Jan Withagen Subject: Re: Very low disk performance Highpoint 1820a X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 08 May 2005 14:29:49 -0000 ---- Original Message ----- From: "Scott Long" > Steven Hartland wrote: >> If that where the case it would have been it wouldn't have been >> 46Mb/s it would have been 543Mb/s, just tested it for you :P > > The RR1280 cards are really just software RAID cards. All of the parity > calculations are done by the CPU. I couldn't find much evidence that > the driver has parity routines that are optimized for the CPU, so it's > likely doing a very inefficient job at it. According to the documentation this is not the case and the XOR calcs are done in hardware on the onboard HPT 601. > Changing MAXPHYS is very dangerous, unfortunately. The root of the > problem is that kernel virtual memory (KVA) gets assigned to each I/O > buffer as it passes through the kernel. If we allow too much I/O through > at once then we have the very real possibility of exhausting the kernel > address space and causing a deadlock and/or panic. That is why MAXPHYS > is set so low. Your DD test is unlikely to trigger a problem, but try > doing a bunch of DD's is parallel and you likely will. Thanks for the heads up on this scott I'll do some tests to see that happens. N.B. I'm currently using 256K instead of 128K which has the same performance increase as using 1M. Note: all tests are being done on i386 not AMD64 due to our requirement for i386 Linux emulation which it is my understanding is not available when running AMD64 FreeBSD. Steve ================================================ This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. In the event of misdirection, illegible or incomplete transmission please telephone (023) 8024 3137 or return the E.mail to postmaster@multiplay.co.uk.