From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756990AbZBGDBW (ORCPT ); Fri, 6 Feb 2009 22:01:22 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753222AbZBGDBE (ORCPT ); Fri, 6 Feb 2009 22:01:04 -0500 Received: from vms173009pub.verizon.net ([206.46.173.9]:46908 "EHLO vms173009pub.verizon.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750745AbZBGDBD (ORCPT ); Fri, 6 Feb 2009 22:01:03 -0500 Date: Fri, 06 Feb 2009 22:00:54 -0500 (EST) From: Len Brown X-X-Sender: lenb@localhost.localdomain To: Ingo Molnar Cc: Ben Greear , Thomas Gleixner , linux-kernel Subject: Re: PATCH: Allow over-ride of smp_found_cfg with kernel cmd-line option. In-reply-to: <20090206193121.GA32634@elte.hu> Message-id: References: <498B421D.9090609@candelatech.com> <20090206193121.GA32634@elte.hu> User-Agent: Alpine 2.00 (LFD 1167 2008-08-23) MIME-version: 1.0 Content-type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > Without this override, performance drops by around 15% on > > network throughput tests on this system. > > The question is, _why_ does network performance drop? > > Do you have a before/after pair of /proc/interrupts output > perhaps? Does the layout of IRQs change? > > The system is not SMP - so only something about UP-IOAPIC can > be helpful to performance here - or some unknown effect. I presume it is IOAPIC (good) vs PIC (bad), for the patch that provoked this regression was one that caused the MPS table to be disabled. (the problem with that patch was that it was effective not just in ACPI mode, but in acpi=off mode) The other un-answered question is why the system under test has ACPI disabled in the BIOS when it did not ship that way from the manufacturer. cheers, -Len Intel Open Source Technology Center