Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756793AbYF0HSQ (ORCPT ); Fri, 27 Jun 2008 03:18:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753149AbYF0HSF (ORCPT ); Fri, 27 Jun 2008 03:18:05 -0400 Received: from e28smtp04.in.ibm.com ([59.145.155.4]:40712 "EHLO e28esmtp04.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751204AbYF0HSD (ORCPT ); Fri, 27 Jun 2008 03:18:03 -0400 Date: Fri, 27 Jun 2008 12:49:48 +0530 From: Vaidyanathan Srinivasan To: Andi Kleen Cc: balbir@linux.vnet.ibm.com, Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Ingo Molnar , Peter Zijlstra , Dipankar Sarma , Vatsa , Gautham R Shenoy Subject: Re: [RFC v1] Tunable sched_mc_power_savings=n Message-ID: <20080627071948.GA15424@dirshya.in.ibm.com> Reply-To: svaidy@linux.vnet.ibm.com Mail-Followup-To: Andi Kleen , balbir@linux.vnet.ibm.com, Linux Kernel , Suresh B Siddha , Venkatesh Pallipadi , Ingo Molnar , Peter Zijlstra , Dipankar Sarma , Vatsa , Gautham R Shenoy References: <20080625191100.GI21892@dirshya.in.ibm.com> <87k5gcqpbm.fsf@basil.nowhere.org> <4863AF57.3040005@linux.vnet.ibm.com> <4863DB29.1020304@firstfloor.org> <20080626185254.GA12416@dirshya.in.ibm.com> <4863F93C.9040102@firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline In-Reply-To: <4863F93C.9040102@firstfloor.org> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1328 Lines: 38 * Andi Kleen [2008-06-26 22:17:00]: > Vaidyanathan Srinivasan wrote: > > Playing devil's advocate here. > [...] > > The > > power QoS framework set_acceptable_latency() ensures that the lowest > > latency set across the system wins. > > But that only helps kernel drivers, not user space, doesn't it? Yes the QoS notification is mainly for kernel drivers, but applications can control them using the /dev/[...,network_latency,...] interface as documented in Documentations/power/pm_qos_interface.txt The device drivers are expected to get feedback (tunable?) from applications that are dependent on those drivers and set the correct power saving level. Multimedia applications are expected to make use of this interface to set/communicate the correct power saving levels for audio drivers. Many application can set different latency requirement, but the least will win. Here the PM-QoS framework in kernel arbitrates between applications and resolves conflicts by choosing the least latency or most conservative power saving mode. --Vaidy [...] -- 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/