From mboxrd@z Thu Jan 1 00:00:00 1970 From: Viresh Kumar Subject: Re: [PATCH V3 12/13] cpufreq: ondemand: Traverse list of policy_dbs in update_sampling_rate() Date: Mon, 8 Feb 2016 19:04:46 +0530 Message-ID: <20160208133446.GK8294@vireshk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: "Rafael J. Wysocki" Cc: Rafael Wysocki , Juri Lelli , Lists linaro-kernel , "linux-pm@vger.kernel.org" , Saravana Kannan , Peter Zijlstra , Michael Turquette , Steve Muckle , Vincent Guittot , Morten Rasmussen , dietmar.eggemann@arm.com, Shilpasri G Bhat , Linux Kernel Mailing List List-Id: linux-pm@vger.kernel.org On 08-02-16, 14:32, Rafael J. Wysocki wrote: > > - * If new rate is smaller than the old, simply updating > > - * dbs_tuners_int.sampling_rate might not be appropriate. For example, if the > > - * original sampling_rate was 1 second and the requested new sampling rate is 10 > > - * ms because the user needs immediate reaction from ondemand governor, but not > > - * sure if higher frequency will be required or not, then, the governor may > > - * change the sampling rate too late; up to 1 second later. Thus, if we are > > - * reducing the sampling rate, we need to make the new value effective > > - * immediately. > > The comment still applies. Why? It talks about the case where we have reduced sampling rate, but that's not the case anymore. We *always* update sample_delay_ns now. > Moreover, please extend it to say that this must be called with > dbs_data->mutex held (or it looks racy otherwise). Yeah, that can be done.