Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Tue, 17 Sep 2002 17:22:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Tue, 17 Sep 2002 17:22:16 -0400 Received: from pizda.ninka.net ([216.101.162.242]:28803 "EHLO pizda.ninka.net") by vger.kernel.org with ESMTP id ; Tue, 17 Sep 2002 17:22:15 -0400 Date: Tue, 17 Sep 2002 14:18:06 -0700 (PDT) Message-Id: <20020917.141806.49377410.davem@redhat.com> To: alan@lxorguk.ukuu.org.uk Cc: ak@suse.de, linux-kernel@vger.kernel.org, johnstul@us.ibm.com, anton.wilson@camotion.com Subject: Re: do_gettimeofday vs. rdtsc in the scheduler From: "David S. Miller" In-Reply-To: <1032298092.20498.21.camel@irongate.swansea.linux.org.uk> References: <20020917.135451.49037528.davem@redhat.com> <1032298092.20498.21.camel@irongate.swansea.linux.org.uk> X-Mailer: Mew version 2.1 on Emacs 21.1 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 879 Lines: 19 From: Alan Cox Date: 17 Sep 2002 22:28:12 +0100 A bus clock - but things like the x440 have more than one bus clock. Its NUMA. Also the bus clock and rdtsc clock are different - rdtsc is dependant on the multiplier. Shove a celeron 300 and a celeron 450 in a BP6 board with tsc on and enjoy That's mostly my point. If the bus clocks differ, then great create some system wide crystal oscillator. That's a detail, the important bit is that you don't need to go out to the system bus to read the tick value, it must be cpu local to be effective and without serious performance impact. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/