From owner-freebsd-current@FreeBSD.ORG Mon Oct 31 07:58:52 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 0FDD016A41F; Mon, 31 Oct 2005 07:58:52 +0000 (GMT) (envelope-from obrien@NUXI.com) Received: from dragon.NUXI.org (trang.nuxi.com [66.93.134.19]) by mx1.FreeBSD.org (Postfix) with ESMTP id 6EC7F43D46; Mon, 31 Oct 2005 07:58:51 +0000 (GMT) (envelope-from obrien@NUXI.com) Received: from dragon.NUXI.org (obrien@localhost [127.0.0.1]) by dragon.NUXI.org (8.13.4/8.13.4) with ESMTP id j9V7wmsB010818; Sun, 30 Oct 2005 23:58:49 -0800 (PST) (envelope-from obrien@dragon.NUXI.org) Received: (from obrien@localhost) by dragon.NUXI.org (8.13.4/8.13.1/Submit) id j9V7whTP010805; Sun, 30 Oct 2005 23:58:43 -0800 (PST) (envelope-from obrien) Date: Sun, 30 Oct 2005 23:58:43 -0800 From: "David O'Brien" To: Scott Long Message-ID: <20051031075843.GF39253@dragon.NUXI.org> Mail-Followup-To: freebsd-current@freebsd.org, Scott Long , Alexander Leidinger , David Xu References: <30595.1130493297@critter.freebsd.dk> <20051028153457.d0wqgn2ask4sgw4k@netchild.homeip.net> <20051029195703.GB39253@dragon.NUXI.org> <43646AAC.2080107@freebsd.org> <20051030093718.GE39253@dragon.NUXI.org> <4364D90F.3090205@samsco.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4364D90F.3090205@samsco.org> X-Operating-System: FreeBSD 7.0-CURRENT Organization: The NUXI BSD Group X-Pgp-Rsa-Fingerprint: B7 4D 3E E9 11 39 5F A3 90 76 5D 69 58 D9 98 7A X-Pgp-Rsa-Keyid: 1024/34F9F9D5 User-Agent: Mutt/1.5.9i Cc: Alexander Leidinger , freebsd-current@freebsd.org, David Xu 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 Reply-To: freebsd-current@freebsd.org List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 31 Oct 2005 07:58:52 -0000 On Sun, Oct 30, 2005 at 07:30:39AM -0700, Scott Long wrote: > David O'Brien wrote: > >On Sun, Oct 30, 2005 at 02:39:40PM +0800, David Xu wrote: > >>David O'Brien wrote: > >>>On Fri, Oct 28, 2005 at 03:34:57PM +0200, Alexander Leidinger wrote: > >>> > >>>>I don't have the message at hand. I just had time to write the mail, > >>>>but I > >>>>don't have my laptop with me to reproduce the message. But it's easy to > >>>>reproduce, just take a PC which is able to make use of powerd and > >>>>switch to > >>>>using TSC as the timecounter. > >>> > >>>What is the motivation to use the TSC as a timecounter? > >> > >>TSC is faster than any others, on many systems, so-called ACPI-fast > >>timer is really a slow chip, > > > >Correct, but why is it felt the latency of the ACPI timer is an issue? > >Of course we all want things to as fast as possible, but is that just an > >abstract desire, or a real issue was run into? > > ACPI-fast requires an ioport read which takes about 1us (according to > Google). Do that 1000 times a second and you have each CPU spending > 1% of its time doing nothing but reading the clock. Yikes. But we've lived with using the ACPI timercounter (vs. TSC) for quite a while now. Why all of a sudden are the authors of this thread having an issue with it now. I know about the recent MySQL thread - but with the TSC being untrustable on MP and power managed systems, why is there such a desire to use the TSC? -- -- David (obrien@FreeBSD.org)