From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda1.sgi.com [192.48.157.11]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q713tpmw244689 for ; Tue, 31 Jul 2012 22:55:51 -0500 Received: from greer.hardwarefreak.com (mo-65-41-216-221.sta.embarqhsd.net [65.41.216.221]) by cuda.sgi.com with ESMTP id oyhtvTzBLVxHiz81 for ; Tue, 31 Jul 2012 20:55:50 -0700 (PDT) Message-ID: <5018A8C7.8050406@hardwarefreak.com> Date: Tue, 31 Jul 2012 22:55:51 -0500 From: Stan Hoeppner MIME-Version: 1.0 Subject: Re: realtime section bugs still around References: <20120730030333.GE2877@dastard> <50186E51.1020107@hardwarefreak.com> In-Reply-To: Reply-To: stan@hardwarefreak.com List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Jason Newton Cc: xfs@oss.sgi.com On 7/31/2012 6:55 PM, Jason Newton wrote: > On Tue, Jul 31, 2012 at 4:46 PM, Stan Hoeppner wrote: > >> On 7/31/2012 6:01 PM, Jason Newton wrote: >> >>> I'm still interested in finding out why streaming a few hundred MB to >> disk >>> has so much over head in comparison to the calculations I do in >> userspace, >> >> 1. md eats a lot of cycles at high data rates >> > > md with intel's raid0? I stopped using linux/softraid, but I've read > intel's is a mix between hardware and software raid... Intel Matrix RAID is fakeraid. Designed for consumer workloads. You're shoving a decidedly non consumer, high b/w IO stream through it. Don't expect much. In fact I'm surprised you're using consumer grade gear for this application. You are designing this software/system for a commercial use case, correct? If so I'd get some better hardware. CPU overhead for fakeraid will be similar to md/RAID, depending on the vendor and implementation. In some cases it may be much higher than md. > 2. ATA overhead >> 3. IRQ/MSI overhead >> 4. Etc. >> >> All these small bits add up to more than negligible CPU overhead at high >> data rates. >> > > Regarding the others, how would I go about measuring their overhead... To what end? -- Stan _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs