From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754569AbZINHon (ORCPT ); Mon, 14 Sep 2009 03:44:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752996AbZINHom (ORCPT ); Mon, 14 Sep 2009 03:44:42 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:49872 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751246AbZINHol (ORCPT ); Mon, 14 Sep 2009 03:44:41 -0400 Date: Mon, 14 Sep 2009 00:43:01 -0700 From: Andrew Morton To: Arjan van de Ven Cc: linux-kernel@vger.kernel.org, lenb@kernel.org, mingo@elte.hu, peterz@infradead.org, yanmin_zhang@linux.intel.com, torvalds@linux-foundation.org, jens.axboe@oracle.com, Tejun Heo , Ingo Molnar , David Howells , Ivan Kokshaysky Subject: Re: PATCH] cpuidle: A new variant of the menu governor to boost IO performance Message-Id: <20090914004301.105196cc.akpm@linux-foundation.org> In-Reply-To: <20090911174019.1ed02737@infradead.org> References: <20090911174019.1ed02737@infradead.org> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Sep 2009 17:40:19 +0200 Arjan van de Ven wrote: > From: Arjan van de Ven > Subject: [PATCH] cpuidle: A new variant of the menu governor > > This patch adds a new idle governor which balances power savings, > energy efficiency and performance impact. > > The reason for a reworked governor is that there have been > serious performance issues reported with the existing code > on Nehalem server systems. > > To show this I'm sure Andrew wants to see benchmark results: > (benchmark is "fio", "no cstates" is using "idle=poll") > > no cstates current linux new algorithm > 1 disk 107 Mb/s 85 Mb/s 105 Mb/s > 2 disks 215 Mb/s 123 Mb/s 209 Mb/s > 12 disks 590 Mb/s 320 Mb/s 585 Mb/s > > In various power benchmark measurements, no degredation was found > by our measurement&diagnostics team. Obviously a bit more power was > used in the "fio" benchmark, due to the much higher performance. > > The integration plan for this is to first add the new governor, > but for one kernel generation, leave the old menu governor in place > so that it's possible to separate out behavior from this governor > versus other things in diagnostics. If no issues are found, > I'll remove the old governor in the kernel cycle after that. > > While it would be a novel idea to describe the new algorithm in this > commit message, I cheaped out and described it in comments in the > code instead. This fails to compile in linux-next: drivers/cpuidle/governors/menu-tng.o:(.discard+0x0): multiple definition of `__pcpu_unique_menu_devices' drivers/cpuidle/governors/menu.o:(.discard+0x0): first defined here because we have static DEFINE_PER_CPU(struct menu_device, menu_devices); in both menu.c and menu-tng.c. Despite the `static', the percpu changes in commit 7c756e6e19e71f0327760d8955f7077118ebb2b1 Author: Tejun Heo AuthorDate: Wed Jun 24 15:13:50 2009 +0900 Commit: Tejun Heo CommitDate: Wed Jun 24 15:13:50 2009 +0900 percpu: implement optional weak percpu definitions are emitting global symbol derived from `menu_devices' and they clash. I'll rename menu_devices to fix that up, but we have a problem...