Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762874AbYHERm5 (ORCPT ); Tue, 5 Aug 2008 13:42:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754954AbYHERms (ORCPT ); Tue, 5 Aug 2008 13:42:48 -0400 Received: from gprs189-60.eurotel.cz ([160.218.189.60]:2399 "EHLO spitz.ucw.cz" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754030AbYHERms (ORCPT ); Tue, 5 Aug 2008 13:42:48 -0400 Date: Tue, 5 Aug 2008 19:42:18 +0200 From: Pavel Machek To: Andreas Herrmann Cc: Len Brown , Thomas Gleixner , LKML , Ingo Molnar , Arjan van de Veen , "Maciej W. Rozycki" Subject: Re: [patch 0/6] AMD C1E aware idle support Message-ID: <20080805174217.GC8380@ucw.cz> References: <20080610171639.551369443@linutronix.de> <20080704143536.GA21102@alberich.amd.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080704143536.GA21102@alberich.amd.com> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 35 Hi! > > > AMD CPUs with C1E support are currently excluded from high resolution > > > timers and NOHZ support. The reason is that C1E is a BIOS controlled > > > C3 power state which switches off TSC and the local APIC timer. The > > > ACPI C-State control manages the TSC/local APIC timer wreckage, but > > > this does not include the C1 based ("halt" instruction) C1E mode. The > > > BIOS/SMM controlled C1E state works on most systems even without > > > enabling ACPI C-State control. > > > > What a mess. Yep, seems like AMD is breaking C1 semantics. Is it even valid from ACPI spec point of view? > > What is the measured power savings that justifies this effort? > > IMHO the power savings are not that important when such a kernel runs > on bare metal: Ok, so maybe we should disable C1E to work around its misdesign? It would be certainly nice to have noc1e command line option... > But overall no measurable difference in power usage was seen. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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/