Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753103AbZDVBGy (ORCPT ); Tue, 21 Apr 2009 21:06:54 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752176AbZDVBGo (ORCPT ); Tue, 21 Apr 2009 21:06:44 -0400 Received: from mga03.intel.com ([143.182.124.21]:49453 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752084AbZDVBGo (ORCPT ); Tue, 21 Apr 2009 21:06:44 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.40,227,1239001200"; d="scan'208";a="134210469" Subject: Re: [RFC PATCH v2 0/2] sched: Nominate a power-efficient ILB From: Suresh Siddha Reply-To: suresh.b.siddha@intel.com To: Gautham R Shenoy Cc: Ingo Molnar , Peter Zijlstra , Vaidyanathan Srinivasan , "linux-kernel@vger.kernel.org" , Balbir Singh , Andi Kleen , Randy Dunlap In-Reply-To: <20090414045356.7645.33369.stgit@sofia.in.ibm.com> References: <20090414045356.7645.33369.stgit@sofia.in.ibm.com> Content-Type: text/plain Organization: Intel Corp Date: Tue, 21 Apr 2009 18:05:22 -0700 Message-Id: <1240362322.27006.8548.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.24.1 (2.24.1-2.fc10) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1432 Lines: 31 On Mon, 2009-04-13 at 21:55 -0700, Gautham R Shenoy wrote: > Now, the other power-savings settings such as the sched_mc/smt_power_savings > and the power-aware IRQ balancer try to balance tasks/IRQs by taking > the system topology into consideration, with the intention of keeping > as many "power-domains" (cores/packages) in the low-power state. > > The current idle-load-balancer nomination does not necessarily align towards > this policy. For eg, we could be having tasks and interrupts largely running > on the first package with the intention of keeping the second package idle. > Hence, CPU 0 may be busy. The first_cpu in the nohz.cpu_mask happens to be CPU1, > which in-turn becomes nominated as the idle-load balancer. CPU1 being from > the 2nd package, would in turn prevent the 2nd package from going into a > deeper sleep state. > > Instead the role of the idle-load balancer could have been assumed by an > idle CPU from the first package, thereby helping the second package go > completely idle. Can we also do this by default? i.e., even when no power-savings policy is selected. I don't see anything wrong by enabling this logic for all the cases. thanks, suresh -- 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/