From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [git pull request] ACPI Processor Aggregator Driver for 2.6.32-rc1 Date: Mon, 5 Oct 2009 21:59:24 +0200 Message-ID: <200910052159.24920.rjw@sisk.pl> References: <20091005033256.GA26592@balbir.in.ibm.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-path: Received: from ogre.sisk.pl ([217.79.144.158]:48659 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752213AbZJET6y (ORCPT ); Mon, 5 Oct 2009 15:58:54 -0400 In-Reply-To: <20091005033256.GA26592@balbir.in.ibm.com> Sender: linux-acpi-owner@vger.kernel.org List-Id: linux-acpi@vger.kernel.org To: balbir@linux.vnet.ibm.com Cc: Len Brown , Linus Torvalds , Andrew Morton , Linux Kernel Mailing List , linux-acpi@vger.kernel.org, Peter Zijlstra , Shaohua Li , Vaidyanathan Srinivasan On Monday 05 October 2009, Balbir Singh wrote: > * Len Brown [2009-10-03 01:56:32]: > > > This driver does not use the kernel's CPU hot-plug mechanism > > because after the transient emergency is over, the system must > > be returned to its normal state, and hotplug would permanently > > break both cpusets and binding. > > > > Why does hotplug break cpusets and binding? > > > > So to force idle, the driver creates a power saving thread. > > The scheduler will migrate the thread to the preferred CPU. > > The thread has max priority and has SCHED_RR policy, > > so it can occupy one CPU. To save power, the thread will > > invoke the deep C-state entry instructions. > > > > To avoid starvation, the thread will sleep 5% of the time > > time for every second (current RT scheduler has threshold > > to avoid starvation, but if other CPUs are idle, > > the CPU can borrow CPU timer from other, > > which makes the mechanism not work here) > > > > Vaidyanathan Srinivasan has proposed scheduler enhancements > > to allow injecting idle time into the system. This driver doesn't > > depend on those enhancements, but could cut over to them > > when they are available. > > > > Peter Z. does not favor upstreaming this driver until > > the those scheduler enhancements are in place. However, > > we favor upstreaming this driver now because it is useful > > now, and can be enhanced over time. > > > > Signed-off-by: Shaohua Li > > NACKed-by: Peter Zijlstra > > Cc: Vaidyanathan Srinivasan > > Signed-off-by: Len Brown > > This is a first a patch with a NACKed-by, could we please have more > discussion on the proposed design. This thing has already been merged, it appears: commit 8e0af5141ab950b78b3ebbfaded5439dcf8b3a8d Author: Shaohua Li Date: Mon Jul 27 18:11:02 2009 -0400 ACPI: create Processor Aggregator Device driver and it looks like a total breakage of rules to me. Thanks, Rafael