From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030468AbXDWDn7 (ORCPT ); Sun, 22 Apr 2007 23:43:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030580AbXDWDn7 (ORCPT ); Sun, 22 Apr 2007 23:43:59 -0400 Received: from mx3.mail.elte.hu ([157.181.1.138]:41235 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030468AbXDWDn6 (ORCPT ); Sun, 22 Apr 2007 23:43:58 -0400 Date: Mon, 23 Apr 2007 05:43:10 +0200 From: Ingo Molnar To: Nick Piggin Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Andrew Morton , Con Kolivas , Mike Galbraith , Arjan van de Ven , Peter Williams , Thomas Gleixner , caglar@pardus.org.tr, Willy Tarreau , Gene Heskett , Mark Lord , Ulrich Drepper Subject: Re: [patch] CFS scheduler, -v5 Message-ID: <20070423034310.GA19845@elte.hu> References: <20070420140457.GA14017@elte.hu> <20070423011229.GA20367@elte.hu> <20070423012509.GA25162@wotan.suse.de> <20070423025553.GA10407@elte.hu> <20070423032215.GC25162@wotan.suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070423032215.GC25162@wotan.suse.de> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.0.3 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Nick Piggin wrote: > > note that CFS's "granularity" value is not directly comparable to > > "timeslice length": > > Right, but it does introduce the kbuild regression, [...] Note that i increased the granularity from 1msec to 5msecs after your kbuild report, could you perhaps retest kbuild with the default settings of -v5? > [...] and as we discussed, this will be only worse on newer CPUs with > bigger caches or less naturally context switchy workloads. yeah - but they'll all be quad core, so the SMP timeslice multiplicator should do the trick. Most of the CFS testers use single-CPU systems. > > (in -v6 i'll scale the granularity up a bit with the number of CPUs, > > like SD does. That should get the right result on larger SMP boxes > > too.) > > I don't really like the scaling with SMP thing. The cache effects are > still going to be significant on small systems, and there are lots of > non-desktop users of those (eg. clusters). CFS using clusters will want to tune the granularity up drastically anyway, to 1 second or more, to maximize throughput. I think a small default with a scale-up-on-SMP rule is pretty sane. We'll gather some more kbuild data and see what happens, ok? > > while i agree it's a tad too finegrained still, I agree with Con's > > choice: rather err on the side of being too finegrained and lose > > some small amount of throughput on cache-intense workloads like > > compile jobs, than err on the side of being visibly too choppy for > > users on the desktop. > > So cfs gets too choppy if you make the effective timeslice comparable > to mainline? it doesnt in any test i do, but again, i'm erring on the side of it being more interactive. Ingo