From owner-freebsd-hackers@FreeBSD.ORG Wed Mar 19 21:46:01 2008 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A32B31065670 for ; Wed, 19 Mar 2008 21:46:01 +0000 (UTC) (envelope-from mwm-keyword-freebsdhackers2.e313df@mired.org) Received: from mired.org (student.mired.org [66.92.153.77]) by mx1.freebsd.org (Postfix) with ESMTP id 4108B8FC29 for ; Wed, 19 Mar 2008 21:46:01 +0000 (UTC) (envelope-from mwm-keyword-freebsdhackers2.e313df@mired.org) Received: (qmail 27865 invoked by uid 1001); 19 Mar 2008 17:45:19 -0400 Received: from bhuda.mired.org (192.168.195.1) by bhuda.mired.org (tmda-ofmipd) with ESMTP; Wed, 19 Mar 2008 17:45:18 -0400 Date: Wed, 19 Mar 2008 17:45:18 -0400 To: Erik Trulsson Message-ID: <20080319174518.202d241c@bhuda.mired.org> In-Reply-To: <20080319203311.GA71206@owl.midgard.homeip.net> References: <47DF1045.6050202@chuckr.org> <20080318082816.GA74218@eos.sc1.parodius.com> <47E146F9.5060105@chuckr.org> <20080319172213.GA28075@eos.sc1.parodius.com> <47E1558A.2030107@chuckr.org> <20080319203311.GA71206@owl.midgard.homeip.net> Organization: Meyer Consulting X-Mailer: Claws Mail 3.3.1 (GTK+ 2.12.8; amd64-portbld-freebsd7.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Delivery-Agent: TMDA/1.1.12 (Macallan) From: Mike Meyer Cc: Chuck Robey , Jeremy Chadwick , FreeBSD-Hackers Subject: Re: remote operation or admin X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Mar 2008 21:46:01 -0000 On Wed, 19 Mar 2008 21:33:11 +0100 Erik Trulsson wrote: > A system that is written to work in a clustered environment can fairly > easily be moved to run on an SMP machine, but it will do a lot of work > that is not necessary under SMP and thus not make very good use of the > hardware. > Moving from SMP to cluster is more difficult. One can emulate the missing > hardware support in software, but this has a very high overhead. Or one > can rewrite the software completely, which is a lot of work. One way to think of such is that cluster software will typically consist of lots of processes talking to each other over sockets whereas SMP software will typically consist of one process with threads talking to each other through shared memory locations. On an SMP system the cluster software could be rewritten to use shared memory and hence improve performance. Likewise, moving the SMP program into a cluster environment means you have to replace shared objects with proxies that copy things around and coordinate actions. At least one concurrent software development system (Bertrand Meyer's SCOOP) is set up so the developer doesn't worry about those things; the location and communications channels of the objects in the program is specified at launch time. http://www.mired.org/consulting.html Independent Network/Unix/Perforce consultant, email for more information.