Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754718AbXE3R2L (ORCPT ); Wed, 30 May 2007 13:28:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753128AbXE3R16 (ORCPT ); Wed, 30 May 2007 13:27:58 -0400 Received: from homer.mvista.com ([63.81.120.158]:27160 "EHLO gateway-1237.mvista.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753063AbXE3R15 (ORCPT ); Wed, 30 May 2007 13:27:57 -0400 Subject: Re: [PATCH 3/5] lockstat: core infrastructure From: Daniel Walker To: Peter Zijlstra Cc: Ingo Molnar , Steven Rostedt , linux-kernel@vger.kernel.org, Andrew Morton , Bill Huey , Jason Baron , Christoph Hellwig In-Reply-To: <1180545380.2958.1.camel@lappy> 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> Content-Type: text/plain Date: Wed, 30 May 2007 10:25:13 -0700 Message-Id: <1180545913.32594.194.camel@imap.mvista.com> Mime-Version: 1.0 X-Mailer: Evolution 2.8.3 (2.8.3-2.fc6) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1320 Lines: 31 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. In the past I've replace sched_clock() with a clocksource, and there was no noticeable speed different .. Just recently I replaced x86's sched_clock() math with the clocksource math with no noticable difference .. At least not from my benchmarks .. > There is room for both of them. There is room, but we don't need sched_clock() .. Certainly we shouldn't force architectures to implement sched_clock() by calling it a "bug" if it's lowres. Daniel - 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/