From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965981AbXDGWjt (ORCPT ); Sat, 7 Apr 2007 18:39:49 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965961AbXDGWjt (ORCPT ); Sat, 7 Apr 2007 18:39:49 -0400 Received: from mx2.suse.de ([195.135.220.15]:45966 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965975AbXDGWjr (ORCPT ); Sat, 7 Apr 2007 18:39:47 -0400 To: "Andika Triwidada" Cc: linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: Re: CPU offline but power consumption increased? References: <7e0bae390704062123i2dfaf030icd5a710677bc989a@mail.gmail.com> From: Andi Kleen Date: 08 Apr 2007 01:38:14 +0200 In-Reply-To: <7e0bae390704062123i2dfaf030icd5a710677bc989a@mail.gmail.com> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org "Andika Triwidada" writes: [cc linux-acpi] > Question: is that normal? I thought power consumption will be > automatically reduced if one core offlined. The current cpu offline essentially just runs a special idle loop. The standard idle loop is even a bit more aggressive on some systems because it knows about the deeper ACPI sleep modi. There are also dependencies between cores because current CPUs have shared power planes between cores. I suppose in the future when a whole socket goes off line one could implement special code to turn off the CPU further. But it likely won't work on older hardware. -Andi