Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754521AbZJEUkS (ORCPT ); Mon, 5 Oct 2009 16:40:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754257AbZJEUkQ (ORCPT ); Mon, 5 Oct 2009 16:40:16 -0400 Received: from e28smtp05.in.ibm.com ([59.145.155.5]:49581 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754206AbZJEUkO (ORCPT ); Mon, 5 Oct 2009 16:40:14 -0400 Date: Tue, 6 Oct 2009 02:03:37 +0530 From: Balbir Singh To: "Rafael J. Wysocki" Cc: Len Brown , Linus Torvalds , Andrew Morton , Linux Kernel Mailing List , linux-acpi@vger.kernel.org, Peter Zijlstra , Shaohua Li , Vaidyanathan Srinivasan Subject: Re: [git pull request] ACPI Processor Aggregator Driver for 2.6.32-rc1 Message-ID: <20091005203337.GB3551@balbir.in.ibm.com> Reply-To: balbir@linux.vnet.ibm.com References: <20091005033256.GA26592@balbir.in.ibm.com> <200910052159.24920.rjw@sisk.pl> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <200910052159.24920.rjw@sisk.pl> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2654 Lines: 67 * Rafael J. Wysocki [2009-10-05 21:59:24]: > 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: > Yeah.. just saw it in my kernel compile today! > 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 -- Balbir -- 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/