From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_NEOMUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF437C43613 for ; Fri, 21 Jun 2019 10:22:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C290620675 for ; Fri, 21 Jun 2019 10:22:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726229AbfFUKWH (ORCPT ); Fri, 21 Jun 2019 06:22:07 -0400 Received: from foss.arm.com ([217.140.110.172]:57588 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726210AbfFUKWH (ORCPT ); Fri, 21 Jun 2019 06:22:07 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0AE921478; Fri, 21 Jun 2019 03:22:06 -0700 (PDT) Received: from queper01-lin (queper01-lin.cambridge.arm.com [10.1.195.48]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 06FF13F718; Fri, 21 Jun 2019 03:22:04 -0700 (PDT) Date: Fri, 21 Jun 2019 11:22:03 +0100 From: Quentin Perret To: Patrick Bellasi Cc: Douglas Raillard , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, dietmar.eggemann@arm.com Subject: Re: [RFC PATCH 1/7] PM: Introduce em_pd_get_higher_freq() Message-ID: <20190621102201.kuid47xl5pi72c4y@queper01-lin> References: <20190508174301.4828-1-douglas.raillard@arm.com> <20190508174301.4828-2-douglas.raillard@arm.com> <20190516124200.opxczohjelhvrzmo@e110439-lin> <20190516130148.uhq55ptut47usnae@queper01-lin> <20190516132250.hedtianse7rnk3wq@e110439-lin> <11976c37-65d3-e0c6-034d-cfec9ebb5b49@arm.com> <20190620130439.c3tk7osezd37pfmj@e110439-lin> <20190621101704.pw7oluum4eqgdgzp@queper01-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190621101704.pw7oluum4eqgdgzp@queper01-lin> User-Agent: NeoMutt/20171215 Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On Friday 21 Jun 2019 at 11:17:05 (+0100), Quentin Perret wrote: > On Thursday 20 Jun 2019 at 14:04:39 (+0100), Patrick Bellasi wrote: > > On 19-Jun 17:08, Douglas Raillard wrote: > > > Hi Patrick, > > > > > > On 5/16/19 2:22 PM, Patrick Bellasi wrote: > > > > On 16-May 14:01, Quentin Perret wrote: > > > > > On Thursday 16 May 2019 at 13:42:00 (+0100), Patrick Bellasi wrote: > > > > > > > +static inline unsigned long em_pd_get_higher_freq(struct em_perf_domain *pd, > > > > > > > + unsigned long min_freq, unsigned long cost_margin) > > > > > > > +{ > > > > > > > + unsigned long max_cost = 0; > > > > > > > + struct em_cap_state *cs; > > > > > > > + int i; > > > > > > > + > > > > > > > + if (!pd) > > > > > > > + return min_freq; > > > > > > > + > > > > > > > + /* Compute the maximum allowed cost */ > > > > > > > + for (i = 0; i < pd->nr_cap_states; i++) { > > > > > > > + cs = &pd->table[i]; > > > > > > > + if (cs->frequency >= min_freq) { > > > > > > > + max_cost = cs->cost + (cs->cost * cost_margin) / 1024; > > > > > > ^^^^ > > > > > > ... end here we should probably better use SCHED_CAPACITY_SCALE > > > > > > instead of hard-coding in values, isn't it? > > > > > > > > > > I'm not sure to agree. This isn't part of the scheduler per se, and the > > > > > cost thing isn't in units of capacity, but in units of power, so I don't > > > > > think SCHED_CAPACITY_SCALE is correct here. > > > > > > > > Right, I get the units do not match and it would not be elegant to use > > > > it here... > > > > > > > > > But I agree these hard coded values (that one, and the 512 in one of the > > > > > following patches) could use some motivation :-) > > > > > > > > ... ultimately SCHED_CAPACITY_SCALE is just SCHED_FIXEDPOINT_SCALE, > > > > which is adimensional. Perhaps we should use that or yet another alias > > > > for the same. > > > > > > Would it be a good idea to use SCHED_FIXEDPOINT_SCALE in energy.c ? > > > Since it's not part of the scheduler, maybe there is a scale covering a wider scope, > > > or we can introduce a similar ENERGY_FIXEDPOINT_SCALE in energy_model.h. > > > > Well, in energy_model.c we have references to "capacity" and > > "utilization" which are all SCHED_FIXEDPOINT_SCALE range values. > > That symbol is defined in and we already pull > > in other headers. > > > > So, to me it seems it's not unreasonable to say that we use scheduler > > related concepts and it makes more sense than introducing yet another > > scaling factor. > > > > But that's just my two cents ;) > > Perhaps use this ? > > https://elixir.bootlin.com/linux/latest/source/include/linux/energy_model.h#L43 > Nah, bad idea actually ... Sorry for the noise