From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755828AbYFRTWW (ORCPT ); Wed, 18 Jun 2008 15:22:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752326AbYFRTWN (ORCPT ); Wed, 18 Jun 2008 15:22:13 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:4189 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751855AbYFRTWM (ORCPT ); Wed, 18 Jun 2008 15:22:12 -0400 Date: Wed, 18 Jun 2008 21:21:48 +0200 From: Pavel Machek To: Thomas Gleixner Cc: LKML , Ingo Molnar , Arjan van de Veen , Andreas Herrmann Subject: Re: [patch 6/6] x86: add c1e aware idle function Message-ID: <20080618192148.GA4243@ucw.cz> References: <20080610171639.551369443@linutronix.de> <20080610171712.465591661@linutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080610171712.465591661@linutronix.de> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu 2008-06-12 10:29:00, Thomas Gleixner wrote: > C1E on AMD machines is like C3 but without control from the OS. Up to > now we disabled the local apic timer for those machines as it stops > when the CPU goes into C1E. This excludes those machines from high > resolution timers / dynamic ticks, which hurts especially the X2 based > laptops. > > The current boot time C1E detection has another more serious flaw: > some BIOSes do not enable C1E until the ACPI processor module is > loaded. This causes systems to stop working after that point. > > To work nicely with C1E enabled machines we use a separate idle > function, which checks on idle entry whether C1E was enabled in the > Interrupt Pending Message MSR. This allows us to do timer broadcasting Entering idle is quite a common operation, and reading MSR is quite slow. Is it possible to do better here? What happens if ACPI BIOS toggles MSR on all cpus *while* we are entering idle? This seems inherently racy... Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html