From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030680AbXDLS1U (ORCPT ); Thu, 12 Apr 2007 14:27:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030678AbXDLS1U (ORCPT ); Thu, 12 Apr 2007 14:27:20 -0400 Received: from mx2.suse.de ([195.135.220.15]:35331 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1030680AbXDLS1T (ORCPT ); Thu, 12 Apr 2007 14:27:19 -0400 From: Andi Kleen Organization: SUSE Linux Products GmbH, Nuernberg, GF: Markus Rex, HRB 16746 (AG Nuernberg) To: Andrew Morton Subject: Re: [PATCH] i386 tsc: remove xtime_lock'ing around cpufreq notifier Date: Thu, 12 Apr 2007 20:27:14 +0200 User-Agent: KMail/1.9.6 Cc: Jeremy Fitzhardinge , Daniel Walker , linux-kernel@vger.kernel.org, johnstul@us.ibm.com, tglx@linutronix.de References: <20070411162904.232696302@mvista.com> <461E6FA7.5080605@goop.org> <20070412105559.385789dd.akpm@linux-foundation.org> In-Reply-To: <20070412105559.385789dd.akpm@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200704122027.14926.ak@novell.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 12 April 2007 19:55:59 Andrew Morton wrote: > On Thu, 12 Apr 2007 10:43:03 -0700 > Jeremy Fitzhardinge wrote: > > > Andrew Morton wrote: > > > hm. People (ab)use sched_clock() for all sorts of things nowadays. I wouldn't > > > do anything to degrade it just on behalf of printk-timestamping. > > > > > > > printk was the only non-scheduler-ish use I could find. Are there others? > > > > blktrace. I've seen a couple of trace/debug-style things which use > sched_clock for timestamping event collection. I think lttng does exotic > things with TSCs, performing private skew correction, although that might > have changed now. They should always just store the cpu too and educate the users that only (cpu, timestamp) pairs make sense to compare. That said at least my new sched_clock should not normally show large non differences between CPUs, so it can be usually ignored, but they can happen. I believe some of the already existing sched_clocks() (like the one used on Altix) have the same property. But on VMI/Xen as currently implemented the differences will be large. -Andi