From owner-freebsd-current@FreeBSD.ORG Tue Nov 1 16:01:34 2005 Return-Path: X-Original-To: freebsd-current@FreeBSD.org Delivered-To: freebsd-current@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id BF10916A41F; Tue, 1 Nov 2005 16:01:34 +0000 (GMT) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (vc4-2-0-87.dsl.netrack.net [199.45.160.85]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6ABE843D70; Tue, 1 Nov 2005 16:01:29 +0000 (GMT) (envelope-from imp@bsdimp.com) Received: from localhost (localhost.village.org [127.0.0.1] (may be forged)) by harmony.bsdimp.com (8.13.3/8.13.3) with ESMTP id jA1FxcnR020622; Tue, 1 Nov 2005 08:59:38 -0700 (MST) (envelope-from imp@bsdimp.com) Date: Tue, 01 Nov 2005 08:59:48 -0700 (MST) Message-Id: <20051101.085948.112718728.imp@bsdimp.com> To: rwatson@FreeBSD.org From: "M. Warner Losh" In-Reply-To: <20051101080018.R18382@fledge.watson.org> References: <81213.1130754398@critter.freebsd.dk> <20051031.215329.115777034.imp@bsdimp.com> <20051101080018.R18382@fledge.watson.org> X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0 (harmony.bsdimp.com [127.0.0.1]); Tue, 01 Nov 2005 08:59:39 -0700 (MST) Cc: phk@phk.freebsd.dk, freebsd-current@FreeBSD.org Subject: Re: TSC instead of ACPI: powerd doesn't work anymore (to be expected?) X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Nov 2005 16:01:34 -0000 In message: <20051101080018.R18382@fledge.watson.org> Robert Watson writes: : On Mon, 31 Oct 2005, M. Warner Losh wrote: : : > In message: <81213.1130754398@critter.freebsd.dk> : > "Poul-Henning Kamp" writes: : > : I am going to insist that clock_gettime(CLOCK_REALTIME, CLOCK_UPTIME) : > : remain precise. : > : > 1ms is way too imprecise for the stuff we do at work. We need 3-4 more : > orders of magnitude at a minimum from the time keeping system. Ideally, : > through well documented interfaces. : : While I agree that for many consumers, sub-1ms accuracy is too low, I : suggest that as a vendor of atomic clocks, your company is in fact not the : average consumer of timing information. :-). For the atomic clocks, we use much better hardware to get timing. The requirements for better than 1ms time keeping comes from the process control aspects of our code, not measuring atomic clocks. : One nice thing about the Linux TSC model, despite its limitations, is that : it provides a middle ground between incrementing the clock in ticks and : providing a more continuous measure of time, by allowing interpolation : between ticks. That's a non-sequitor to what I'm talking about.. :-) Warner