From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757436AbYENG6c (ORCPT ); Wed, 14 May 2008 02:58:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752430AbYENG6M (ORCPT ); Wed, 14 May 2008 02:58:12 -0400 Received: from one.firstfloor.org ([213.235.205.2]:57148 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757966AbYENG6K (ORCPT ); Wed, 14 May 2008 02:58:10 -0400 Message-ID: <482A8D7D.7000208@firstfloor.org> Date: Wed, 14 May 2008 08:58:05 +0200 From: Andi Kleen User-Agent: Thunderbird 1.5.0.12 (X11/20060911) MIME-Version: 1.0 To: Arjan van de Ven CC: Vegard Nossum , Ingo Molnar , Thomas Gleixner , Andreas Herrmann , =?windows-1252?Q?=22S=2E=C7?= =?windows-1252?Q?ag=28lar_Onur=22?= , Valdis.Kletnieks@vt.edu, Matt Mackall , linux-kernel@vger.kernel.org, lenb@kernel.org Subject: Re: [BISECTED] Lots of "rescheduling IPIs" in powertop References: <20080513204206.GA17781@damson.getinternet.no> <873aol9b73.fsf@basil.nowhere.org> <19f34abd0805131409w2914fbedgb608c7b87c234e2e@mail.gmail.com> <482A05F3.7020408@firstfloor.org> <20080513210217.59a7ca65@infradead.org> In-Reply-To: <20080513210217.59a7ca65@infradead.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Arjan van de Ven wrote: [cc Len] > On Tue, 13 May 2008 23:19:47 +0200 > Andi Kleen wrote: > >> Ok the CPU reports it doesn't support any C states in MWAIT. If that >> is correct then it would be correct to not use MWAIT idle and might >> actually save more power to not use it. > > what does the current SVN powertop say on this cpu? > >> I don't know if that's true or not. Do you have a power meter perhaps? >> If yes can you measure if there's a difference between mwait=idle / >> default on your box when it is idle? >> >> [cc Arjan he might now if that CPU is supposed to support C1 in MWAIT] > > I wasn't aware that P4's supported mwait in this way; I thought it was > core and later. Not even C1? I generally consider MWAIT without C1 to be unusable. Anyways if C1 doesn't work then it would be correct to not use MWAIT. > >> CPU reports it supports C1/C2/C3. Are you sure there is a difference >> on that box? The code should have kept using MWAIT because it checks >> C1. Please double check. > > The check is .. dubious I suspect... I don't think so. > because the cpuid bits are not > actually the prime source of information, the BIOS is. Hmmm? What BIOS information are you refering to? Normally it's my experience that CPUID is more reliable than the BIOS. > If the bios says mwait is usable, we need to use it with the values IT > gives us. At least to my knowledge the ACPI FADT just says what C states are available, not if they are implemented with MWAIT or using IO ports. -Andi