Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1765492AbXE2Ube (ORCPT ); Tue, 29 May 2007 16:31:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759369AbXE2Ub1 (ORCPT ); Tue, 29 May 2007 16:31:27 -0400 Received: from gateway-1237.mvista.com ([63.81.120.158]:40075 "EHLO gateway-1237.mvista.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759158AbXE2Ub0 (ORCPT ); Tue, 29 May 2007 16:31:26 -0400 Subject: Re: [PATCH 3/5] lockstat: core infrastructure From: Daniel Walker To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Andrew Morton , Ingo Molnar , Bill Huey , Jason Baron , Steven Rostedt , Christoph Hellwig In-Reply-To: <20070529130107.112347096@chello.nl> References: <20070529125248.877196281@chello.nl> <20070529130107.112347096@chello.nl> Content-Type: text/plain Date: Tue, 29 May 2007 13:28:45 -0700 Message-Id: <1180470525.32594.71.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: 858 Lines: 20 On Tue, 2007-05-29 at 14:52 +0200, Peter Zijlstra wrote: > + now = sched_clock(); > + waittime = now - hlock->waittime_stamp; > + It looks like your using sched_clock() through out .. It's a little troubling considering the constraints on the function .. Most architecture implement a jiffies sched_clock() w/ 1 millisecond or worse resolution.. I'd imagine a millisecond hold time is pretty rare, even a millisecond wait time might be fairly rare too .. There's also no guarantee that sched_clock timestamps off two different cpu's can be compared (or at least that's my understanding) .. 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/