From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754783Ab2BEDvD (ORCPT ); Sat, 4 Feb 2012 22:51:03 -0500 Received: from mail-pw0-f46.google.com ([209.85.160.46]:34484 "EHLO mail-pw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753681Ab2BEDvA (ORCPT ); Sat, 4 Feb 2012 22:51:00 -0500 Date: Sat, 4 Feb 2012 19:50:57 -0800 From: mark gross To: "Pihet-XID, Jean" Cc: Venkatesh Pallipadi , "Rafael J. Wysocki" , markgross , Kevin Hilman , linux-kernel@vger.kernel.org, Len Brown , Linux PM mailing list Subject: Re: [PATCH] CPU C-state breakage with PM Qos change Message-ID: <20120205035057.GA4948@gs62> Reply-To: markgross@thegnar.org References: <1328227065-22045-1-git-send-email-venki@google.com> <1328228079-20716-1-git-send-email-venki@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Feb 03, 2012 at 03:04:43PM +0100, Pihet-XID, Jean wrote: > Looping in linux-pm > > On Fri, Feb 3, 2012 at 1:14 AM, Venkatesh Pallipadi wrote: > > Looks like change "PM QoS: Move and rename the implementation files" > > made pm_qos depend on CONFIG_PM which depends on > > PM_SLEEP || PM_RUNTIME > > > > That breaks CPU C-states with kernels not having these CONFIGs, causing CPUs > > to spend time in Polling loop idle instead of going into deep C-states, > > consuming way way more power. This is with either acpi idle or intel idle > > enabled. > > > > Either CONFIG_PM should be enabled with any pm_qos users or > > the !CONFIG_PM pm_qos_request() should return sane defaults not to break > > the existing users. Here's is the patch for the latter option. > I think the real question is whether PM QoS should be functional in > all cases (as is ACPI) or whether only if certain options are set > (CONFIG_PM). > In the current code if CONFIG_PM is not enabled, a dummy PM QoS API is > provided as function stubs in order for the build to succeed. > > Rafael, Mark, > What do you think? Should PM QoS be enabled in all cases? Are there > any known dependencies with CONFIG_PM? Yes I do think pm_qos interfaces should be enabled all the time and be independent of CONFIG_PM. Also, I still am not a fan of the renaming patch but, as the argument for and against renaming cannot be based on quantifiable things I've chosen not to let it bother me. I think Venki's change is a band aid and we should fix it right by not having a dependency on config_pm for the interface to behave. I'll take a look at why there is now a dependency before I have more to say. --mark