From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932518AbXLTSXp (ORCPT ); Thu, 20 Dec 2007 13:23:45 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753009AbXLTSXf (ORCPT ); Thu, 20 Dec 2007 13:23:35 -0500 Received: from pentafluge.infradead.org ([213.146.154.40]:36173 "EHLO pentafluge.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753556AbXLTSXe (ORCPT ); Thu, 20 Dec 2007 13:23:34 -0500 Date: Thu, 20 Dec 2007 10:22:02 -0800 From: Arjan van de Ven To: "H. Peter Anvin" Cc: Ingo Molnar , Venki Pallipadi , Thomas Gleixner , Len Brown , linux-kernel Subject: Re: [PATCH] x86: Voluntary leave_mm before entering ACPI C3 Message-ID: <20071220102202.64f395a7@laptopd505.fenrus.org> In-Reply-To: <476A9576.3020203@zytor.com> References: <20071219183443.GA547@linux-os.sc.intel.com> <20071219193255.GA2158@elte.hu> <476972A0.3050105@zytor.com> <20071219194032.GA8849@elte.hu> <4769757E.306@zytor.com> <20071219235357.53157cea@laptopd505.fenrus.org> <476A9576.3020203@zytor.com> Organization: Intel X-Mailer: Claws Mail 3.0.2 (GTK+ 2.12.1; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by pentafluge.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 20 Dec 2007 08:16:54 -0800 "H. Peter Anvin" wrote: > Arjan van de Ven wrote: > > On Wed, 19 Dec 2007 11:48:14 -0800 > > "H. Peter Anvin" wrote: > > > >> I think C3 guarantees that the cache contents stay intact, and thus > >> it might make sense in some technology to preserve the TLB as well > >> (being a kind of cache.) > > > > that sounds nice. It's fiction though ;-) > > > > The thing to realize is that linux only sees "ACPI C3"; the BIOS > > maps that C3 to.. well any of the C states the processor in the > > system has. What you're saying is afaik correct for the *hardware* > > C3, not for the "C3" that Linux sees.. > > > > Well, it can only map ACPI C3 to a state which is no more "dead" than > what would normally be permitted by C3. IIRC, C3 is allowed to > require that DMA be turned off (unlike C2), but is not allowed to > lose the CPU state. state isn't lost if the tlb or the caches are flushed... (properly, eg all pending writebacks are written back first etc) -- If you want to reach me at my work email, use arjan@linux.intel.com For development, discussion and tips for power savings, visit http://www.lesswatts.org