From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932918Ab3ICNdE (ORCPT ); Tue, 3 Sep 2013 09:33:04 -0400 Received: from mail-bk0-f41.google.com ([209.85.214.41]:37467 "EHLO mail-bk0-f41.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932870Ab3ICNdA (ORCPT ); Tue, 3 Sep 2013 09:33:00 -0400 Message-ID: <5225E508.2060407@linaro.org> Date: Tue, 03 Sep 2013 15:32:56 +0200 From: Daniel Lezcano User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130510 Thunderbird/17.0.6 MIME-Version: 1.0 To: Viresh Kumar CC: "Rafael J. Wysocki" , "linux-pm@vger.kernel.org" , Linux Kernel Mailing List , Lists linaro-kernel , Suresh.Srinivasan@arm.com, Amit Kucheria , Sudeep KarkadaNagesha Subject: Re: [Query-CPUIdle]: Not much activity in C0 state References: In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/27/2013 12:23 PM, Viresh Kumar wrote: > Hi Guys, > > I was trying to run following on my thinkpad: > > watch -n1 cat /sys/devices/system/cpu/cpu*/cpuidle/state*/usage > > I can see lots of activities on State 1-4, but not much on state 0.. > I thought we should enter this state as soon as we come out to > non-idle state.. And so this count must be changing quite rapidly. > > Is this a bug? Hi Viresh, the menu governor tries always to stick to C1 (state1) as default state, look at the menu_select function. The state0 (not C0 but 'poll') will happen when the next timer event is less than 5us, this occurs rarely. You can easily spot it by doing while $(true); usleep 2; done The poll state is x86 specific where the cpu detects the 'rep nop' instructions to do some power saving. Hope that helps -- Daniel -- Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog