From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752922Ab0DTA64 (ORCPT ); Mon, 19 Apr 2010 20:58:56 -0400 Received: from casper.infradead.org ([85.118.1.10]:58150 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751194Ab0DTA6z (ORCPT ); Mon, 19 Apr 2010 20:58:55 -0400 Date: Mon, 19 Apr 2010 18:00:32 -0700 From: Arjan van de Ven To: Peter Zijlstra Cc: Salman Qazi , mingo@elte.hu, linux-kernel@vger.kernel.org, akpm@linux-foundation.org, svaidy@linux.vnet.ibm.com, linux-pm@lists.linux-foundation.org, csadler@google.com, ranjitm@google.com, kenchen@google.com, dawnchen@google.com Subject: Re: [PATCH 0/3] [idled]: Idle Cycle Injector for power capping Message-ID: <20100419180032.15586a90@infradead.org> In-Reply-To: <1271703701.1676.235.camel@laptop> References: <20100413234902.29004.41655.stgit@bumblebee1.mtv.corp.google.com> <1271317886.32749.69.camel@laptop> <1271703701.1676.235.camel@laptop> Organization: Intel X-Mailer: Claws Mail 3.7.5 (GTK+ 2.16.6; i586-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 On Mon, 19 Apr 2010 21:01:41 +0200 Peter Zijlstra wrote: > Right, so the IBM folks who were looking at power aware scheduling > were working on an interface to quantify the amount of power to save. > > But their approach, was an extension of the regular power aware > load-balancer, which basically groups tasks onto sockets so that whole > sockets can go idle. > > However Arjan explained to me that your approach, which idles the > whole machine, has the advantage that also memory banks can go into > idle mode and save power. > > Still in the interest to cut back on power-saving interfaces it would > be nice to see if there is anything we can do to merge these things, > but I really haven't thought much about that yet. one correction, this is not about power *saving*, it is about power *capping*. Power capping is pretty much energy inefficient by definition (and surely in practice), but it's about dealing with reality about underdimensioned airconditioning or voltage rails.... Due to the reality that socket offlining isn't as good as idle insertion.. I rather focus on the later... -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org