Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761410AbXEKM34 (ORCPT ); Fri, 11 May 2007 08:29:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757284AbXEKM3s (ORCPT ); Fri, 11 May 2007 08:29:48 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:1355 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1760083AbXEKM3r (ORCPT ); Fri, 11 May 2007 08:29:47 -0400 Date: Thu, 10 May 2007 13:09:55 +0000 From: Pavel Machek To: Peter Williams Cc: Esben Nielsen , Linus Torvalds , Ingo Molnar , Balbir Singh , linux-kernel@vger.kernel.org, Andrew Morton , Con Kolivas , Nick Piggin , Mike Galbraith , Arjan van de Ven , Thomas Gleixner , caglar@pardus.org.tr, Willy Tarreau , Gene Heskett , Mark Lord , Zach Carter , buddabrod Subject: Re: [patch] CFS scheduler, -v8 Message-ID: <20070510130954.GC4052@ucw.cz> References: <463854F3.3020403@linux.vnet.ibm.com> <20070502100545.GA6857@elte.hu> <46386F2B.9050307@linux.vnet.ibm.com> <20070502111742.GA18132@elte.hu> <20070506082911.GA32644@elte.hu> <463FC5D8.2090502@bigpond.net.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <463FC5D8.2090502@bigpond.net.au> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1714 Lines: 47 Hi! > >>You say there is "no danger of overflow", and I mostly > >>agree that once > >>we're talking about 64-bit values, the overflow issue > >>simply doesn't > >>exist, and furthermore the difference between 63 and > >>64 bits is not really > >>relevant, so there's no major reason to actively avoid > >>signed entries. > >> > >>So in that sense, it all sounds perfectly sane. And > >>I'm definitely not > >>sure your "292 years after bootup" worry is really > >>worth even considering. > >> > > > >I would hate to tell mission control for Mankind's > >first mission to another > >star to reboot every 200 years because "there is no > >need to worry about it." > > > >As a matter of principle an OS should never need a > >reboot (with exception for upgrading). If you say you > >have to reboot every 200 years, why not every 100? > >Every 50? .... Every 45 days (you know what I am > >referring to :-) ? > > There's always going to be an upper limit on the > representation of time. At least until we figure out > how to implement infinity properly. There's also upper limit on life time of this universe. 1000 bits is certainly enough to represent that in u-seconds. Also notice that current cpus were not designed to work 300 years. When we have hw designed for 50 years+, we can start to worry. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html - 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/