From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zhang Rui Subject: Re: [PATCH] intel_powerclamp: Fix cstate counter detection. Date: Thu, 02 Jan 2014 11:03:32 +0800 Message-ID: <1388631812.3739.75.camel@rzhang1-mobl4> References: <1384758395-5074-1-git-send-email-yshuiv7@gmail.com> <528A3EC9.8060301@linux.intel.com> <528B74C9.3010902@linux.intel.com> <20131119103818.2cccaa93@ultegra> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: Received: from mga11.intel.com ([192.55.52.93]:5779 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750958AbaABDDh (ORCPT ); Wed, 1 Jan 2014 22:03:37 -0500 In-Reply-To: <20131119103818.2cccaa93@ultegra> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Jacob Pan Cc: Yuxuan Shui , Arjan van de Ven , linux-pm@vger.kernel.org On Tue, 2013-11-19 at 10:38 -0800, Jacob Pan wrote: > On Wed, 20 Nov 2013 02:09:12 +0800 > Yuxuan Shui wrote: > > > On Tue, Nov 19, 2013 at 10:25 PM, Arjan van de Ven > > wrote: > > > On 11/18/2013 9:29 PM, Yuxuan Shui wrote: > > >> > > >> On Tue, Nov 19, 2013 at 12:22 AM, Arjan van de Ven > > >> wrote: > > >>> > > >>> On 11/17/2013 11:06 PM, Yuxuan Shui wrote: > > >>>> > > >>>> > > >>>> Having all zero cstate count doesn't necesserily mean the cstate > > >>>> counter is no functional. > > >>>> > > >>> > > >>> ... but it does mean that powerclamp will be non-functional > > >>> > > >>> but you had a reason to make this patch. > > >>> Can you expand a little bit on what you were seeing that made you > > >>> decide this patch was needed ? > > >>> > > >> There are possibilities that the system is busy from boot so that > > >> it doesn't enter C-state at all, right? In that situation > > >> powerclamp won't work. > > > > > > > > > > > > that is... extremely unlikely. Have you seen that happen? > > > > Sure I've seen this, that's why I wrote this patch in the first place. > > It's my (rather old) laptop. After boot powertop show zero percent in > > C3 and C6, and powerclamp complaining pkg cstate counter is not > > functional. > > > I see, this is indeed a corner case where the sanity check by powerclamp > driver is too strict and refused to load. I am OK with your patch and > perhaps add a sanity check later while idle injection is in action? > so do you want me to include this patch for 3.14? thanks, rui > > > > > >> > > >> Also, pkg_state_counter is used to calculate a cstate ratio, and I > > >> can't find any reason why powerclamp will be non-funtional when > > >> that ratio is zero. > > > > > > > > > if the counters we use are zero.. we can't use them in our control > > > loop > > > > I skimmed through the code. pkg_state_counter is called twice (except > > that once in start_power_clamp). Once in poll_pkg_cstate to calculate > > pkg_cstate_ratio_cur which is used for sysfs. The other time is in > > powerclamp_adjust_controls, which is used to calculate a ratio which > > is stored in a global variable current_ratio. > > > > The current_ratio is also used twice. Once in the same function, to > > check if we have done enough idle injection. The other is in > > adjust_compensation, where it's used to calculate a delta. In neither > > case current_ratio being zero will matter. > > > > Also, I'm using this patch myself, and it seems to be totally > > functional. > > > > So I failed to see why the counter can't be zero. If I made any > > mistakes, can you point them out? > > > > > > > > > again, what were you actually seeing? > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > [Jacob Pan] > -- > To unsubscribe from this list: send the line "unsubscribe linux-pm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html