Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757310Ab0FDDnH (ORCPT ); Thu, 3 Jun 2010 23:43:07 -0400 Received: from casper.infradead.org ([85.118.1.10]:52555 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756997Ab0FDDnF (ORCPT ); Thu, 3 Jun 2010 23:43:05 -0400 Date: Thu, 3 Jun 2010 20:45:21 -0700 From: Arjan van de Ven To: Linus Torvalds Cc: Ingo Molnar , tytso@mit.edu, Brian Swetland , Neil Brown , Arve Hj?nnev?g , Thomas Gleixner , "Rafael J. Wysocki" , Alan Stern , Felipe Balbi , Peter Zijlstra , LKML , Florian Mickler , Linux OMAP Mailing List , Linux PM , Alan Cox , James Bottomley , Peter Zijlstra , Kevin Hilman , "H. Peter Anvin" Subject: Re: suspend blockers & Android integration Message-ID: <20100603204521.09808a7f@infradead.org> In-Reply-To: References: <20100603193045.GA7188@elte.hu> <20100603231153.GA11302@elte.hu> <20100603232302.GA16184@elte.hu> <20100603234634.GA21831@elte.hu> Organization: Intel X-Mailer: Claws Mail 3.7.6 (GTK+ 2.20.1; 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 casper.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 Content-Length: 1306 Lines: 36 On Thu, 3 Jun 2010 19:26:50 -0700 (PDT) Linus Torvalds wrote: > > If the system is idle (or almost idle) for long times, I would > heartily recommend actively shutting down unused cores. Some CPU's > are hopefully smart enough to not even need that kind of software > management, but I suspect even the really smart ones might be able to > take advantage of the kernel saying: "I'm shutting you down, you > don't have to worry about latency AT ALL, because I'm keeping another > CPU active to do any real work". sadly the reality is that "offline" is actually the same as "deepest C state". At best. As far as I can see, this is at least true for all Intel and AMD cpus. And because there's then no power saving (but a performance cost), it's actually a negative for battery life/total energy. (lots of experiments inside Intel seem to confirm that, it's not just theory) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org -- 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/