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[209.132.180.67]) by mx.google.com with ESMTP id x68-v6si393484pfc.0.2018.11.07.03.39.17; Wed, 07 Nov 2018 03:39:34 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726641AbeKGVIy (ORCPT <rfc822;noahbdev@gmail.com> + 99 others); Wed, 7 Nov 2018 16:08:54 -0500 Received: from foss.arm.com ([217.140.101.70]:49404 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726241AbeKGVIy (ORCPT <rfc822;linux-kernel@vger.kernel.org>); Wed, 7 Nov 2018 16:08:54 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 4B7F780D; Wed, 7 Nov 2018 03:38:55 -0800 (PST) Received: from e110439-lin (e110439-lin.cambridge.arm.com [10.1.194.43]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 7CA533F5CF; Wed, 7 Nov 2018 03:38:52 -0800 (PST) Date: Wed, 7 Nov 2018 11:38:49 +0000 From: Patrick Bellasi <patrick.bellasi@arm.com> To: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Tejun Heo <tj@kernel.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Vincent Guittot <vincent.guittot@linaro.org>, Viresh Kumar <viresh.kumar@linaro.org>, Paul Turner <pjt@google.com>, Quentin Perret <quentin.perret@arm.com>, Dietmar Eggemann <dietmar.eggemann@arm.com>, Morten Rasmussen <morten.rasmussen@arm.com>, Juri Lelli <juri.lelli@redhat.com>, Todd Kjos <tkjos@google.com>, Joel Fernandes <joelaf@google.com>, Steve Muckle <smuckle@google.com>, Suren Baghdasaryan <surenb@google.com> Subject: Re: [PATCH v5 09/15] sched/cpufreq: uclamp: add utilization clamping for FAIR tasks Message-ID: <20181107113849.GC14309@e110439-lin> References: <20181029183311.29175-1-patrick.bellasi@arm.com> <20181029183311.29175-11-patrick.bellasi@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181029183311.29175-11-patrick.bellasi@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org On 29-Oct 18:33, Patrick Bellasi wrote: [...] > +#ifdef CONFIG_UCLAMP_TASK > +/** > + * clamp_util: clamp a utilization value for a specified CPU > + * @rq: the CPU's RQ to get the clamp values from > + * @util: the utilization signal to clamp > + * > + * Each CPU tracks util_{min,max} clamp values depending on the set of its > + * currently RUNNABLE tasks. Given a utilization signal, i.e a signal in > + * the [0..SCHED_CAPACITY_SCALE] range, this function returns a clamped > + * utilization signal considering the current clamp values for the > + * specified CPU. > + * > + * Return: a clamped utilization signal for a given CPU. > + */ > +static inline unsigned int uclamp_util(struct rq *rq, unsigned int util) > +{ > + unsigned int min_util = rq->uclamp.value[UCLAMP_MIN]; > + unsigned int max_util = rq->uclamp.value[UCLAMP_MAX]; Just notice here we can have an issue. For each scheduling entity, we always ensure that: util_min <= util_max However, since CPU's {min,max}_util clamps are always MAX aggregated considering the corresponding clamps of RUNNABLE tasks with _different_ clamps, we can end up with CPU clamps where: util_min > util_max Thus, we need to add the following sanity check here: + if (unlikely(min_util > max_util)) + return min_util; > + > + return clamp(util, min_util, max_util); > +} -- #include <best/regards.h> Patrick Bellasi