Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964784AbWBAAxU (ORCPT ); Tue, 31 Jan 2006 19:53:20 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751273AbWBAAxU (ORCPT ); Tue, 31 Jan 2006 19:53:20 -0500 Received: from liaag1ac.mx.compuserve.com ([149.174.40.29]:52200 "EHLO liaag1ac.mx.compuserve.com") by vger.kernel.org with ESMTP id S1751259AbWBAAxT (ORCPT ); Tue, 31 Jan 2006 19:53:19 -0500 Date: Tue, 31 Jan 2006 19:50:17 -0500 From: Chuck Ebbert <76306.1226@compuserve.com> Subject: Re: boot-time slowdown for measure_migration_cost To: "Luck, Tony" Cc: Bjorn Helgaas , Ingo Molnar , linux-ia64 , linux-kernel , Linus Torvalds , Andrew Morton , "Chen, Kenneth W" Message-ID: <200601311952_MC3-1-B742-9F59@compuserve.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1440 Lines: 38 In-Reply-To: <20060130200026.GA5081@agluck-lia64.sc.intel.com> On Mon, 30 Jan 2006, Tony Luck wrote: > Might it be wise to see whether the 2% variation that I saw can be > repeated on some other architecture? Bjorn's initial post was just > questioning whether we need to spend this much time during boot to acquire > this data. Now we have *one* data point that on an ia64 with four cpus > with 9MB cache in a single domain that we can speed the calculation by > a factor of three with only a 2% loss of accuracy. Can someone else try > this patch and post the before/after values for migration_cost from dmesg? Before: messages.1:Jan 24 01:19:45 d2 kernel: [ 6.377117] migration_cost=9352 messages.1:Jan 27 21:07:55 d2 kernel: [ 6.384871] migration_cost=9329 messages.1:Jan 28 11:00:32 d2 kernel: [ 6.384215] migration_cost=9338 messages.1:Jan 28 12:55:03 d2 kernel: [ 6.389189] migration_cost=9364 After: messages:Jan 31 07:55:07 d2 kernel: [ 1.859359] migration_cost=9274 This was on a dual PII Xeon with 2MB L2 cache. About 3.5x as fast and only 1% change. Maybe the default could be to run the quick test with an option to run the more-accurate one? -- Chuck - 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/