From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263171AbVGNWud (ORCPT ); Thu, 14 Jul 2005 18:50:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263164AbVGNWuI (ORCPT ); Thu, 14 Jul 2005 18:50:08 -0400 Received: from clock-tower.bc.nu ([81.2.110.250]:62339 "EHLO lxorguk.ukuu.org.uk") by vger.kernel.org with ESMTP id S263170AbVGNWsx (ORCPT ); Thu, 14 Jul 2005 18:48:53 -0400 Subject: Re: [PATCH] i386: Selectable Frequency of the Timer Interrupt From: Alan Cox To: Linus Torvalds Cc: john stultz , Arjan van de Ven , Vojtech Pavlik , Lee Revell , dean gaudet , Chris Wedgwood , Andrew Morton , Len Brown , dtor_core@ameritech.net, david.lang@digitalinsight.com, davidsen@tmr.com, kernel@kolivas.org, lkml , mbligh@mbligh.org, diegocg@gmail.com, azarah@nosferatu.za.org, christoph@lameter.com In-Reply-To: References: <1121286258.4435.98.camel@mindpipe> <20050713134857.354e697c.akpm@osdl.org> <20050713211650.GA12127@taniwha.stupidest.org> <20050714005106.GA16085@taniwha.stupidest.org> <1121304825.4435.126.camel@mindpipe> <1121326938.3967.12.camel@laptopd505.fenrus.org> <20050714121340.GA1072@ucw.cz> <1121360561.3967.55.camel@laptopd505.fenrus.org> <1121370122.7673.161.camel@cog.beaverton.ibm.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Message-Id: <1121381026.3747.14.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.6 (1.4.6-2) Date: Thu, 14 Jul 2005 23:43:48 +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Iau, 2005-07-14 at 21:13, Linus Torvalds wrote: > There is no way to avoid having some kind of counter to specify time. > NONE. The only choice is what you base your notion of time on, and how you > represent it. Do you represent it as two separate counters and try to make > it look like "fractions of seconds", or do you represent it as a single > counter, and make it look like "ticks". I suspect the problem for some of this is that people think of jiffies as incrementing by 1. If HZ is right then jiffies can be in nS, it just won't increment by 1. Its also why jiffies() is better on some platforms because many machines can answer "what time is it" far more accurately than they can set interrupts.