From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtuBoQn6h8zc3lpmwBCJfnAjB8Lz7pHIgGHAUye43EmtfVNMdkHiB2arNpyeBj0RB//+biI ARC-Seal: i=1; a=rsa-sha256; t=1521635967; cv=none; d=google.com; s=arc-20160816; b=aSMLmeMYdJ9aXTSZIxtj8e5reh4yCK8VhTaVNZYpqasIm4TSQ5N9Ty58eby0FLzXL2 b5fL+0DK4WVgLVQZQTToImL7pYx3Gur2bhc5MNbeYqEBJ2f/MUA8kdu8YfwIhmZuxCcZ ZdEEvxesVP+JMSw/yjrKF/w6mgI47o61KG0TlrzYQx4gkSEUR9dxiEM7KAuVU0+xFjZg GmKFvogCo8KWY6kBuHPmWFSx0ugGjWs9FVX928mfJW1Z3rFD4sPa9tNBkt4oKbqE77qF FA6Mc2NJ4IM3JSM/G/kf+HIIYsZw7aRjpLz0P3RtmmXPC1gRrtD8gdBR+D//M3V915Wz UJCA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=user-agent:in-reply-to:content-disposition:mime-version:references :message-id:subject:cc:to:from:date:arc-authentication-results; bh=1q0R0iv4VaKynwK23Ou8w7NS+/MdjYN6ev2Ly57oo80=; b=qzksZUWyJnuE7yYP4DkHd9MwWhphTHcq4tP9+i3SrpwJR2JKLtMz39c0b6s3koEgW8 BrIvnhXf/IxUcKMQ1h7H6u3V7myJ/GF/PWbWpDCEq+pBen9dzx136fnaeRquOGJB4oYL IKanmtBj57/7FwqmLZYGFiNvCQhtsTk8PFWEvNjzX/DaHzRV8MptGLecW6QZO/x0Cck0 rJYBxCyBBSUGQf05IEXpRmcjMX7tKFY60nJs+7M9usqFyVTigy8lnxAOB/50Tg9PfNSQ hF6RD84rfECrUCpBeLdZ6uUGWufD04H4LHGYZ5rOIj4G0O2DhtHh/j2bnRMQ5dAm0DV7 g5aw== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: domain of patrick.bellasi@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=patrick.bellasi@arm.com Authentication-Results: mx.google.com; spf=pass (google.com: domain of patrick.bellasi@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=patrick.bellasi@arm.com Date: Wed, 21 Mar 2018 12:39:21 +0000 From: Patrick Bellasi To: Dietmar Eggemann Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Quentin Perret , Thara Gopinath , linux-pm@vger.kernel.org, Morten Rasmussen , Chris Redpath , Valentin Schneider , "Rafael J . Wysocki" , Greg Kroah-Hartman , Vincent Guittot , Viresh Kumar , Todd Kjos , Joel Fernandes Subject: Re: [RFC PATCH 4/6] sched/fair: Introduce an energy estimation helper function Message-ID: <20180321123921.GB13951@e110439-lin> References: <20180320094312.24081-1-dietmar.eggemann@arm.com> <20180320094312.24081-5-dietmar.eggemann@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180320094312.24081-5-dietmar.eggemann@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595449339672655930?= X-GMAIL-MSGID: =?utf-8?q?1595550955946328774?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 20-Mar 09:43, Dietmar Eggemann wrote: > From: Quentin Perret [...] > +static unsigned long compute_energy(struct task_struct *p, int dst_cpu) > +{ > + unsigned long util, fdom_max_util; > + struct capacity_state *cs; > + unsigned long energy = 0; > + struct freq_domain *fdom; > + int cpu; > + > + for_each_freq_domain(fdom) { > + fdom_max_util = 0; > + for_each_cpu_and(cpu, &(fdom->span), cpu_online_mask) { > + util = cpu_util_next(cpu, p, dst_cpu); Would be nice to find a way to cache all these util and reuse them below... even just to ensure data consistency between the "cs" computation and its usage... > + fdom_max_util = max(util, fdom_max_util); > + } > + > + /* > + * Here we assume that the capacity states of CPUs belonging to > + * the same frequency domains are shared. Hence, we look at the > + * capacity state of the first CPU and re-use it for all. > + */ > + cpu = cpumask_first(&(fdom->span)); > + cs = find_cap_state(cpu, fdom_max_util); ^^^^ The above code could theoretically return NULL, although likely EAS is completely disabled if em->nb_cap_states == 0, right? If that's the case then, in the previous function, you can certainly avoid the initialization of *cs and maybe also add an explicit: BUG_ON(em->nb_cap_states == 0); which helps even just as "in code documentation". But, I'm not sure if maintainers like BUG_ON in scheduler code :) > + > + /* > + * The energy consumed by each CPU is derived from the power ^ Should we make more explicit that this is just the "active" energy consumed? > + * it dissipates at the expected OPP and its percentage of > + * busy time. > + */ > + for_each_cpu_and(cpu, &(fdom->span), cpu_online_mask) { > + util = cpu_util_next(cpu, p, dst_cpu); > + energy += cs->power * util / cs->cap; > + } > + } nit-pick: empty line before return? > + return energy; > +} > + > /* > * select_task_rq_fair: Select target runqueue for the waking task in domains > * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE, > -- > 2.11.0 > -- #include Patrick Bellasi