From owner-freebsd-hackers@FreeBSD.ORG Tue Feb 28 16:54:45 2006 Return-Path: X-Original-To: freebsd-hackers@freebsd.org Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8A4AE16A420 for ; Tue, 28 Feb 2006 16:54:45 +0000 (GMT) (envelope-from babkin@verizon.net) Received: from vms046pub.verizon.net (vms046pub.verizon.net [206.46.252.46]) by mx1.FreeBSD.org (Postfix) with ESMTP id 4C09A43D49 for ; Tue, 28 Feb 2006 16:54:45 +0000 (GMT) (envelope-from babkin@verizon.net) Received: from vms061.mailsrvcs.net ([192.168.1.2]) by vms046.mailsrvcs.net (Sun Java System Messaging Server 6.2-4.02 (built Sep 9 2005)) with ESMTPA id <0IVE00FKBPN839FB@vms046.mailsrvcs.net> for freebsd-hackers@freebsd.org; Tue, 28 Feb 2006 10:54:44 -0600 (CST) Date: Tue, 28 Feb 2006 10:54:44 -0600 (CST) From: Sergey Babkin To: David Malone , Vlad GALU Message-id: <15896416.1141145684582.JavaMail.root@vms061.mailsrvcs.net> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1 Content-transfer-encoding: 7bit X-Mailman-Approved-At: Tue, 28 Feb 2006 17:37:18 +0000 Cc: freebsd hackers Subject: Re: Re: Fastest timecounter ? X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: babkin@users.sf.net List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 28 Feb 2006 16:54:45 -0000 >From: David Malone >The TSC is always fastest, but unfortunately under some circumstances >it can't be trusted (if your CPU has throttle modes to save power >or on some SMP systems where the two TSCs in each CPU give different >values). If I remember correctly, all the SMP CPUs on the same bus should give the same values (since they are synchronized and reset from the same signals). The discrepancy may appear on machines with multiple bridged front-side buses, essentially the NUMA machines (such as those with over 4 Intel CPUs). -SB