From owner-freebsd-arch@FreeBSD.ORG Wed Sep 19 02:15:17 2007 Return-Path: Delivered-To: arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8A9C516A41B for ; Wed, 19 Sep 2007 02:15:17 +0000 (UTC) (envelope-from jroberson@chesapeake.net) Received: from webaccess-cl.virtdom.com (webaccess-cl.virtdom.com [216.240.101.25]) by mx1.freebsd.org (Postfix) with ESMTP id 3263813C483 for ; Wed, 19 Sep 2007 02:15:17 +0000 (UTC) (envelope-from jroberson@chesapeake.net) Received: from [192.168.1.103] (c-67-160-44-208.hsd1.wa.comcast.net [67.160.44.208]) (authenticated bits=0) by webaccess-cl.virtdom.com (8.13.6/8.13.6) with ESMTP id l8J2FDlM024012 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES256-SHA bits=256 verify=NO); Tue, 18 Sep 2007 22:15:16 -0400 (EDT) (envelope-from jroberson@chesapeake.net) Date: Tue, 18 Sep 2007 19:18:05 -0700 (PDT) From: Jeff Roberson X-X-Sender: jroberson@10.0.0.1 To: Garrett Wollman In-Reply-To: <200709190143.l8J1hJKA074148@hergotha.csail.mit.edu> Message-ID: <20070918191527.C558@10.0.0.1> References: <20070917165657.B558@10.0.0.1> <46EF644E.9050207@elischer.org> <20070918012555.G558@10.0.0.1> <46EFE4BD.4030505@freebsd.org> <20070918142115.C558@10.0.0.1> <200709190143.l8J1hJKA074148@hergotha.csail.mit.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: arch@freebsd.org Subject: Re: 64bit ticks, was Re: Changing p_swtime and td_slptime to ticks X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Sep 2007 02:15:17 -0000 On Tue, 18 Sep 2007, Garrett Wollman wrote: > Jeff Roberson writes: > >> Is there a good reason for not making ticks 64bit? math involving this >> value is relatively infrequent. Bruce? Any comments? It'd sure let us >> forget all of these counter wrapping problems. > > Making ticks 64 bits on 32-bit architectures means that updates to it > will not be atomic. You're right. There would be a chance that you'd get mismatched upper and lower halves on wrap conditions and would have to detect accordingly. That's probably too much trouble. Thanks, Jeff > > -GAWollman > > -- > Garrett A. Wollman | The real tragedy of human existence is not that we are > wollman@csail.mit.edu| nasty by nature, but that a cruel structural asymmetry > Opinions not those | grants to rare events of meanness such power to shape > of MIT or CSAIL. | our history. - S.J. Gould, Ten Thousand Acts of Kindness >