From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753254AbYGVOCk (ORCPT ); Tue, 22 Jul 2008 10:02:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750770AbYGVOCb (ORCPT ); Tue, 22 Jul 2008 10:02:31 -0400 Received: from smtpq2.tilbu1.nb.home.nl ([213.51.146.201]:42982 "EHLO smtpq2.tilbu1.nb.home.nl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750718AbYGVOCb (ORCPT ); Tue, 22 Jul 2008 10:02:31 -0400 Message-ID: <4885E8F8.1050207@keyaccess.nl> Date: Tue, 22 Jul 2008 16:04:40 +0200 From: Rene Herman User-Agent: Thunderbird 2.0.0.14 (X11/20080421) MIME-Version: 1.0 To: Arjan van de Ven CC: David Woodhouse , linux-kernel@vger.kernel.org, Thomas Gleixner , Ingo Molnar , Stephen Hemminger Subject: Re: [RFC] Imprecise timers. References: <1216695757.18980.16.camel@shinybook.infradead.org> <488589E6.5070300@keyaccess.nl> <20080722055421.2023d261@infradead.org> In-Reply-To: <20080722055421.2023d261@infradead.org> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -1.0 (-) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22-07-08 14:54, Arjan van de Ven wrote: > On Tue, 22 Jul 2008 09:19:02 +0200 > Rene Herman wrote: > >> On 22-07-08 05:02, David Woodhouse wrote: >> >>> Many users of timers don't really care too much about exactly when >>> their timer fires -- and waking a CPU to satisfy such a timer is a >>> waste of power. This patch implements a 'range' timer which will >>> fire at a 'convenient' moment within given constraints. >>> >>> It's implemented by a deferrable timer at the beginning of the >>> range, which will run some time later when the CPU happens to be >>> awake. And a non-deferrable timer at the hard deadline, to ensure >>> it really does happen by then. >> Are there actually users for this (not just in theory)? The >> deferrable timer sort of sounds like all I'd ever want if I, as you >> say, wouldn't really care... > > there's a few; mostly around hardware timeout..For example Stephen want > it for his drivers. Hardware I've dealt with is (almost? can't remember anything else) exlusively minimal delays and as such this thing seemed like perhaps a bit over-apisized... > EXT3 journal flushing is another one where we can easily say > "between 4 and 7 seconds" rather than "exactly at 5" This a nice-ish example though. It might be considered necessary to make the current commit delay when set explicitly be the non-deferrable upper bound but almost none do I guess. Rene.