Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261406AbTKTKVU (ORCPT ); Thu, 20 Nov 2003 05:21:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261509AbTKTKVU (ORCPT ); Thu, 20 Nov 2003 05:21:20 -0500 Received: from aun.it.uu.se ([130.238.12.36]:57776 "EHLO aun.it.uu.se") by vger.kernel.org with ESMTP id S261406AbTKTKVT (ORCPT ); Thu, 20 Nov 2003 05:21:19 -0500 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <16316.38292.729957.491201@alkaid.it.uu.se> Date: Thu, 20 Nov 2003 11:21:08 +0100 From: Mikael Pettersson To: john stultz Cc: Chris Friesen , linux-kernel Subject: Re: high res timestamps and SMP In-Reply-To: <1069297341.23568.130.camel@cog.beaverton.ibm.com> References: <3FBBF148.20203@nortelnetworks.com> <1069297341.23568.130.camel@cog.beaverton.ibm.com> X-Mailer: VM 7.17 under Emacs 20.7.1 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 902 Lines: 21 john stultz writes: > On Wed, 2003-11-19 at 14:40, Chris Friesen wrote: > > We have a requirement to have high-res timestamps available on SMP systems. ... > o PPC has a nice in-cpu time-base register (ppc folks, feel free to > smack or correct me on this) which is driven off the bus-clock and is > synced in hardware. Last time I checked, all 32-bit PowerPC chips ran that clock at 1/4 of the bus clock speed. That may be adequate for time-of-day and I/O delays and such, but it's worthless for timestamps or performance measurements. It's possible to count core clocks via a performance counter, but I don't know if they are synced between CPUs. - 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/