From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukasz Majewski Subject: Re: [PATCH v4 5/7] cpufreq: Calculate number of busy CPUs Date: Fri, 28 Jun 2013 08:54:57 +0200 Message-ID: <20130628085457.05d64878@amdc308.digital.local> References: <1370502472-7249-1-git-send-email-l.majewski@samsung.com> <1371661969-7660-1-git-send-email-l.majewski@samsung.com> <1371661969-7660-6-git-send-email-l.majewski@samsung.com> <20130627125819.5c90da30@amdc308.digital.local> <20130627164204.370dc4a6@amdc308.digital.local> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-reply-to: Sender: linux-pm-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Viresh Kumar Cc: "Rafael J. Wysocky" , "cpufreq@vger.kernel.org" , Linux PM list , Vincent Guittot , Jonghwa Lee , Myungjoo Ham , linux-kernel , Lukasz Majewski , Andre Przywara , Daniel Lezcano , Kukjin Kim , Zhang Rui , Eduardo Valentin On Fri, 28 Jun 2013 09:20:40 +0530, Viresh Kumar wrote: > On 27 June 2013 20:12, Lukasz Majewski wrote: > > On Thu, 27 Jun 2013 16:46:44 +0530, Viresh Kumar wrote: > >> @Rafael: We need you to jump into this discussion now, I don't > >> have a good idea about what we should do :) > >> > >> On 27 June 2013 16:28, Lukasz Majewski > >> wrote: > >> > Do you have any idea of how to precisely set the load threshold? > >> > >> I thought we are talking about cpu being in idle state. > > > > If we _drop_ the idea with thermal subsystem to disable the boost, > > the logic as far as I've understood shall here be as follow: > > > > Only enable BOOST when one CPU load > THRESHOLD_MAX and other CPUs < > > THRESHOLD_MIN > > Again, I thought that we are talking about cpus being completely idle. > i.e. in WFI (wait for interrupt) or deeper states. > > > THRESHOLD_MIN & THRESHOLD_MAX are SoC specific. > > > > In my opinion the above constrain imposes policy to the cpufreq > > driver. > > Hmm. > > > So thermal or "other solution" [*] shall disable boost when > > overheated and enable it back when things cool down. > > yeah.. For me thermal is a good candidate to enable boost again. I only need to find a proper place for it. > > > [*] @ Viresh & Rafael do you have any idea about the "other > > solution" here? > > Not really sure :) Not any single one? Then I would like to propose thermal. > > >> There might be platforms where overheating isn't a issue with > >> boost, if it is only enabled while only one cpu is in use. > > > > Could you elaborate more on this? > > I meant platforms where chip doesn't heat up much when only one core > is in use and is using boost frequency. So, they may not require > support for thermal layer at all.. But I am not aware of what the > ground reality is. If such systems can be possible or not. Ok. > > > This would prevent situation when somebody made a mistake and > > had enabled boost, but for some reason had forgotten to > > configure/enable thermal subsystem. > > > > Moreover Kconfig's CONFIG_CPUFREQ_BOOST flag would indicate that > > user enabled boost for some reason and he/she (presumably) knows > > what is doing. > > Yeah.. And drivers like ACPI cpufreq and exynos can simply do a select > from their Kconfig entries so that user isn't required to select them. Automatic select is not a good option. My goal would be here to define BOOST as NO by default (at lease for SW managed ones). And allow user to enable it explicitly. -- Best regards, Lukasz Majewski Samsung R&D Institute Poland (SRPOL) | Linux Platform Group