From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cuda.sgi.com (cuda2.sgi.com [192.48.176.25]) by oss.sgi.com (8.14.3/8.14.3/SuSE Linux 0.8) with ESMTP id q0K8ramw093659 for ; Fri, 20 Jan 2012 02:53:36 -0600 Received: from Ishtar.sc.tlinx.org (ishtar.tlinx.org [173.164.175.65]) by cuda.sgi.com with ESMTP id 4UveIOijSnnyNMnz for ; Fri, 20 Jan 2012 00:53:35 -0800 (PST) Message-ID: <4F192B8C.1050406@tlinx.org> Date: Fri, 20 Jan 2012 00:53:32 -0800 From: Linda Walsh MIME-Version: 1.0 Subject: Re: concurrent direct IO write in xfs References: <20120116232549.GC6922@dastard> In-Reply-To: List-Id: XFS Filesystem from SGI List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: xfs-bounces@oss.sgi.com Errors-To: xfs-bounces@oss.sgi.com To: Zheng Da , Linux-Xfs Zheng Da wrote: > > I create a file of 4GB in XFS (the ramdisk has 5GB of space). My test > program overwrites 4G of data to the file ---- It sounds like you are asking why multiple threads don't move memory from one point to another point in memory at a faster rate than one thread alone. I.e. if you had 2 processes doing an assembly instruction, memmov to move a chunk of memory from 1 area to another, would you expect to do the move any faster if you had 2 processors doing the move vs. 1?? I think the limiting factor (unless you have a slow processor and some REALLY fast memory, but stock x86-64 parts, today have memory running about 2-4 times slower than the processor -- so the memory is usually the bottleneck. Two processes wouldn't do it any faster, and might actually do it slower due to resource contention issues -- I would *think*... but I really don't know the details of how writing from mem2mem and having the target be in the format of and xfs file system, would cause cpu-bound delays that would be significant to change the fact that m2m operations are usually mem-bandwidth limited...? (I don't know the answers, just clarifying what you are asking)... _______________________________________________ xfs mailing list xfs@oss.sgi.com http://oss.sgi.com/mailman/listinfo/xfs