From owner-p4-projects Thu Jan 2 12:13:30 2003 Delivered-To: p4-projects@freebsd.org Received: by hub.freebsd.org (Postfix, from userid 32767) id D8A9737B405; Thu, 2 Jan 2003 12:13:28 -0800 (PST) Delivered-To: perforce@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 68EA937B401; Thu, 2 Jan 2003 12:13:28 -0800 (PST) Received: from kayak.xcllnt.net (209-128-86-226.BAYAREA.NET [209.128.86.226]) by mx1.FreeBSD.org (Postfix) with ESMTP id 73E7C43E4A; Thu, 2 Jan 2003 12:13:27 -0800 (PST) (envelope-from marcel@xcllnt.net) Received: from dhcp01.pn.xcllnt.net (dhcp01.pn.xcllnt.net [192.168.4.201]) by kayak.xcllnt.net (8.12.6/8.12.6) with ESMTP id h02KDMrT029317; Thu, 2 Jan 2003 12:13:22 -0800 (PST) (envelope-from marcel@kayak.pn.xcllnt.net) Received: from dhcp01.pn.xcllnt.net (localhost [127.0.0.1]) by dhcp01.pn.xcllnt.net (8.12.6/8.12.6) with ESMTP id h02KEbLL000677; Thu, 2 Jan 2003 12:14:37 -0800 (PST) (envelope-from marcel@dhcp01.pn.xcllnt.net) Received: (from marcel@localhost) by dhcp01.pn.xcllnt.net (8.12.6/8.12.6/Submit) id h02KEb4P000676; Thu, 2 Jan 2003 12:14:37 -0800 (PST) (envelope-from marcel) Date: Thu, 2 Jan 2003 12:14:37 -0800 From: Marcel Moolenaar To: John Baldwin Cc: Perforce Change Reviews Subject: Re: PERFORCE change 23029 for review Message-ID: <20030102201437.GB616@dhcp01.pn.xcllnt.net> References: <200301012203.h01M3nKH028011@repoman.freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.1i Sender: owner-p4-projects@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On Thu, Jan 02, 2003 at 10:59:30AM -0500, John Baldwin wrote: > > On 01-Jan-2003 Marcel Moolenaar wrote: > > http://perforce.freebsd.org/chv.cgi?CH=23029 > > > > Change 23029 by marcel@marcel_nfs on 2003/01/01 14:03:34 > > > > While here, reload cr.itm (interval timer match register) > > based on the old value of cr.itm and not cr.itc (interval > > timer counter). The value of cr.itc is non-deterministicly > > close to the value of cr.itm at the time of the interrupt. > > The SDM clearly states that they are not guaranteed to be > > identical, even though the interrupt is triggered when > > cr.itc equals cr.itm). Reloading cr.itm based on the value > > of cr.itc will therefore introduce a non-deterministic error > > in the clocks. This will also reduce clock skew due to > > interrupt latency. > > Cool. Peter says the Linux code does something similar but goes > to extra efforts to handle the case of missing entire ticks and > what not.w Yeah, that hit me after committing and I noticed that sparc64 does that too. As you have probably seen, I reverted the change for now. A missed clock interrupt is worse than a slight error. Doug got me a bit confused though, so I won't touch the code until I deconfused myself :-) -- Marcel Moolenaar USPA: A-39004 marcel@xcllnt.net To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe p4-projects" in the body of the message