Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756684AbXE3RQw (ORCPT ); Wed, 30 May 2007 13:16:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752471AbXE3RQp (ORCPT ); Wed, 30 May 2007 13:16:45 -0400 Received: from viefep18-int.chello.at ([213.46.255.22]:37781 "EHLO viefep12-int.chello.at" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753257AbXE3RQo (ORCPT ); Wed, 30 May 2007 13:16:44 -0400 Subject: Re: [PATCH 3/5] lockstat: core infrastructure From: Peter Zijlstra To: Daniel Walker Cc: Ingo Molnar , Steven Rostedt , linux-kernel@vger.kernel.org, Andrew Morton , Bill Huey , Jason Baron , Christoph Hellwig In-Reply-To: <1180544796.32594.184.camel@imap.mvista.com> 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> Content-Type: text/plain Date: Wed, 30 May 2007 19:16:20 +0200 Message-Id: <1180545380.2958.1.camel@lappy> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1689 Lines: 37 On Wed, 2007-05-30 at 10:06 -0700, Daniel Walker wrote: > On Wed, 2007-05-30 at 15:49 +0200, Ingo Molnar wrote: > > * Steven Rostedt wrote: > > > > > [...] We can argue that sched_clock is "good enough". If someone > > > wants better accounting of locks on some other arch, they can simply > > > change sched_clock to be more precise. > > > > exactly. Imprecise sched_clock() if there's a better fast clock source > > available is a bug in the architecture code. If the only available > > clocksource is 1 msec resolution then there's no solution and nothing to > > talk about - lock statistics will be 1msec granular just as much as > > scheduling. > > > I don't agree .. sched_clock() is obsoleted by timekeepings clocksource > structure.. sched_clock() was a quick way to get lowlevel time stamps > just for the scheduler. The timekeeping clocksource structure is a more > complete solution. > > >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. There is room for both of them. - 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/