Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759943AbXFAN3r (ORCPT ); Fri, 1 Jun 2007 09:29:47 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757138AbXFAN3k (ORCPT ); Fri, 1 Jun 2007 09:29:40 -0400 Received: from mx2.suse.de ([195.135.220.15]:39132 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757066AbXFAN3i (ORCPT ); Fri, 1 Jun 2007 09:29:38 -0400 To: Daniel Walker Cc: Peter Zijlstra , Ingo Molnar , Steven Rostedt , linux-kernel@vger.kernel.org, Andrew Morton , Bill Huey , Jason Baron , Christoph Hellwig Subject: Re: [PATCH 3/5] lockstat: core infrastructure References: <20070529125248.877196281@chello.nl> <20070529130107.112347096@chello.nl> <1180470525.32594.71.camel@imap.mvista.com> <20070530132431.GA23947@elte.hu> <20070530134907.GA27085@elte.hu> <1180544796.32594.184.camel@imap.mvista.com> <1180545380.2958.1.camel@lappy> <1180545913.32594.194.camel@imap.mvista.com> From: Andi Kleen Date: 01 Jun 2007 16:25:47 +0200 In-Reply-To: <1180545913.32594.194.camel@imap.mvista.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1099 Lines: 21 Daniel Walker writes: > On Wed, 2007-05-30 at 19:16 +0200, Peter Zijlstra wrote: > > > > >From the architecture perspective there are two low level clock hooks to > > > implement one is sched_clock() , and at least one clocksource structure. > > > Both do essentially the same thing. With timekeepings clocksource > > > structure actually being easier to implement cause the math is built in. > > > > I think you are mistaken here; the two are similar but not identical. > > > > I see sched_clock() as fast first, accurate second. Whereas the > > clocksource thing is accurate first, fast second. > > This is true .. However, if there is a speed different it's small. pmtimer (factor 1000+) or HPET (factor 10-100+ depending on CPU) accesses are much slower than TSC or jiffies read. Talking to the southbridge is slow. -Andi - 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/