Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965075AbVJ1E1R (ORCPT ); Fri, 28 Oct 2005 00:27:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965077AbVJ1E1R (ORCPT ); Fri, 28 Oct 2005 00:27:17 -0400 Received: from mail06.syd.optusnet.com.au ([211.29.132.187]:38889 "EHLO mail06.syd.optusnet.com.au") by vger.kernel.org with ESMTP id S965075AbVJ1E1Q (ORCPT ); Fri, 28 Oct 2005 00:27:16 -0400 From: Con Kolivas To: Jesper Juhl Subject: Re: The "best" value of HZ Date: Fri, 28 Oct 2005 14:29:39 +1000 User-Agent: KMail/1.8.3 Cc: Lee Revell , Alistair John Strachan , Claudio Scordino , linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org References: <200510280118.42731.cloud.of.andor@gmail.com> <1130471136.4363.29.camel@mindpipe> <9a8748490510272100u453e73e3mc957a673eeb8498e@mail.gmail.com> In-Reply-To: <9a8748490510272100u453e73e3mc957a673eeb8498e@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200510281429.39532.kernel@kolivas.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2131 Lines: 44 On Fri, 28 Oct 2005 02:00 pm, Jesper Juhl wrote: > On 10/28/05, Lee Revell wrote: > > On Fri, 2005-10-28 at 03:31 +0100, Alistair John Strachan wrote: > > > On Friday 28 October 2005 00:18, Claudio Scordino wrote: > > > > Hi, > > > > > > > > during the last years there has been a lot of discussion about > > > > the "best" value of HZ... On i386 was 100, then became 1000, and > > > > finally was set to 250. I'm thinking to do an evaluation of this > > > > parameter using different architectures. > > > > > > > > Has anybody thought to give the possibility to modify the value of HZ > > > > at boot time instead of at compile time ? This would allow to easily > > > > test different values on different machines and create a table > > > > containing the "best" value for each architecture... At this moment, > > > > instead, we have to recompile the kernel for each different value :( > > > > > > > > Do you think there would be much work to do that ? > > > > Do you think it would be a desired feature the knowledge of the best > > > > value for each architecture with more precision ? > > > > > > Google for "dynticks". There's obviously an overhead associated with HZ > > > not being a constant (the compiler cannot optimise many expressions), > > > but the feature is being worked on nonetheless. > > > > Well Linus had the best idea in that thread (as usual) which was to > > implement "dynamic ticks" by leaving HZ a constant, setting it to a high > > value, and skipping ticks when idle. Has there been any work in that > > direction? > > i did a bit of work in that area, but the stuff I came up with never > seemed to work right, so I dropped it. It's all still in development at the moment but not far from being available again. We stood back a bit to make some structural changes before trying to make it ready for prime time. Cheers, Con - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/