From owner-freebsd-hackers@FreeBSD.ORG Thu Dec 22 22:33:14 2005 Return-Path: X-Original-To: freebsd-hackers@freebsd.org 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 45D7C16A41F for ; Thu, 22 Dec 2005 22:33:14 +0000 (GMT) (envelope-from cracauer@schlepper.zs64.net) Received: from schlepper.zs64.net (schlepper.zs64.net [212.12.50.230]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6F5CA43D5A for ; Thu, 22 Dec 2005 22:33:13 +0000 (GMT) (envelope-from cracauer@schlepper.zs64.net) Received: from schlepper.zs64.net (schlepper [212.12.50.230]) by schlepper.zs64.net (8.13.3/8.12.9) with ESMTP id jBMMXCgP024157; Thu, 22 Dec 2005 23:33:12 +0100 (CET) (envelope-from cracauer@schlepper.zs64.net) Received: (from cracauer@localhost) by schlepper.zs64.net (8.13.3/8.12.9/Submit) id jBMMX8VA024153; Thu, 22 Dec 2005 17:33:08 -0500 (EST) (envelope-from cracauer) Date: Thu, 22 Dec 2005 17:33:08 -0500 From: Martin Cracauer To: Kris Kennaway Message-ID: <20051222173308.B23728@cons.org> References: <43A26FFB.9080405@samsco.org> <20051216104022.A20877@cons.org> <20051217063409.GB19094@silverwraith.com> <20051217080109.GA31849@xor.obsecurity.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <20051217080109.GA31849@xor.obsecurity.org>; from kris@obsecurity.org on Sat, Dec 17, 2005 at 03:01:09AM -0500 Cc: freebsd-hackers@freebsd.org Subject: Re: My wish list for 6.1 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: Thu, 22 Dec 2005 22:33:14 -0000 Kris Kennaway wrote on Sat, Dec 17, 2005 at 03:01:09AM -0500: > On Fri, Dec 16, 2005 at 10:34:09PM -0800, Avleen Vig wrote: > > On Fri, Dec 16, 2005 at 10:40:22AM -0500, Martin Cracauer wrote: > > > > 2. SMP kernels for install. Right now we only install a UP kernel, for > > > > performance reasons. We should be able to package both a UP and SMP > > > > kernel into the release bits, and have sysinstall install both. It > > > > should also select the correct one for the target system and make that > > > > the default on boot. > > > > > > If people are concerned about performance, I benchmarked a 6-beta > > > kernel SMP versus UP on a socket 939 Opteron. > > > > If those results are accurate, there's no real reason not to just use an > > SMP kernel on default install? > > Just because it didn't manifest on this workload, doesn't mean it > doesn't on others. I think this is the point :) I tried to model different worklods. The parallel part of my benchmark suite has CPU-heavy processes, short plain http, php, long plain http and mixtures thereof. None of these showed the SMP kernel to be an overall disadvantage on a one-processor system. However, the tradeoffs are different. The SMP kernel further increases the tendency that FreeBSD had all along to give CPU eaters more resources, disk and network I/O less, compared to Linux. Whether this is good or bad is open for discussion. From a traffic control standpoint you can both argue that it is better to get the CPU demands out of the way instead of getting more I/O done only to have the I/Oing processes then pile up in the already overcrowded CPU-demanding corner - and you can argue that you should get I/O done ASAP so that the I/O-initiating process doesn't hang around neccessaryily long. This is for both schedulers. I don't think this tendency is directly caused by the scheduler, it is probably the I/O subsystems coercing the scheduler, not the other way round. Martin -- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer http://www.cons.org/cracauer/ FreeBSD - where you want to go, today. http://www.freebsd.org/