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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 00BF9C433B4 for ; Thu, 15 Apr 2021 15:32:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BDD4F61152 for ; Thu, 15 Apr 2021 15:32:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233598AbhDOPdB (ORCPT ); Thu, 15 Apr 2021 11:33:01 -0400 Received: from foss.arm.com ([217.140.110.172]:49444 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231137AbhDOPc6 (ORCPT ); Thu, 15 Apr 2021 11:32:58 -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 347C5106F; Thu, 15 Apr 2021 08:32:35 -0700 (PDT) Received: from [10.57.24.156] (unknown [10.57.24.156]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 20BA93FA35; Thu, 15 Apr 2021 08:32:32 -0700 (PDT) Subject: Re: [PATCH] PM / EM: Inefficient OPPs detection To: Quentin Perret Cc: Vincent Donnefort , peterz@infradead.org, rjw@rjwysocki.net, viresh.kumar@linaro.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, ionela.voinescu@arm.com, dietmar.eggemann@arm.com References: <1617901829-381963-1-git-send-email-vincent.donnefort@arm.com> <1617901829-381963-2-git-send-email-vincent.donnefort@arm.com> <20210415143453.GB391924@e120877-lin.cambridge.arm.com> <20210415151446.GC391924@e120877-lin.cambridge.arm.com> From: Lukasz Luba Message-ID: Date: Thu, 15 Apr 2021 16:32:31 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Quentin, On 4/15/21 4:20 PM, Quentin Perret wrote: > On Thursday 15 Apr 2021 at 16:14:46 (+0100), Vincent Donnefort wrote: >> On Thu, Apr 15, 2021 at 02:59:54PM +0000, Quentin Perret wrote: >>> On Thursday 15 Apr 2021 at 15:34:53 (+0100), Vincent Donnefort wrote: >>>> On Thu, Apr 15, 2021 at 01:16:35PM +0000, Quentin Perret wrote: >>>>> On Thursday 08 Apr 2021 at 18:10:29 (+0100), Vincent Donnefort wrote: >>>>>> --- a/kernel/sched/cpufreq_schedutil.c >>>>>> +++ b/kernel/sched/cpufreq_schedutil.c >>>>>> @@ -10,6 +10,7 @@ >>>>>> >>>>>> #include "sched.h" >>>>>> >>>>>> +#include >>>>>> #include >>>>>> #include >>>>>> >>>>>> @@ -164,6 +165,9 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, >>>>>> >>>>>> freq = map_util_freq(util, freq, max); >>>>>> >>>>>> + /* Avoid inefficient performance states */ >>>>>> + freq = em_pd_get_efficient_freq(em_cpu_get(policy->cpu), freq); >>>>> >>>>> I remember this was discussed when Douglas sent his patches some time >>>>> ago, but I still find it sad we index the EM table here but still >>>>> re-index the cpufreq frequency table later :/ >>>>> >>>>> Yes in your case this lookup is very inexpensive, but still. EAS relies >>>>> on the EM's table matching cpufreq's accurately, so this second lookup >>>>> still feels rather unnecessary ... >>>> >>>> To get only a single lookup, we would need to bring the inefficiency knowledge >>>> directly to the cpufreq framework. But it has its own limitations: >>>> >>>> The cpufreq driver can have its own resolve_freq() callback, which means that >>>> not all the drivers would benefit from that feature. >>>> >>>> The cpufreq_table can be ordered and accessed in several ways which brings >>>> many combinations that would need to be supported, ending-up with something >>>> much more intrusive. (We can though decide to limit the feature to the low to >>>> high access that schedutil needs). >>>> >>>> As the EM needs schedutil to exist anyway, it seemed to be the right place for >>>> this code. It allows any cpufreq driver to benefit from the feature, simplify a >>>> potential extension for a usage by devfreq devices and as a bonus it speeds-up >>>> energy computing, allowing a more complex Energy Model. >>> >>> I was thinking of something a bit simpler. cpufreq_driver_resolve_freq >>> appears to be used only from schedutil (why is it even then?), so we >>> could just pull it into cpufreq_schedutil.c and just plain skip the call >>> to cpufreq_frequency_table_target if the target freq has been indexed in >>> the EM table -- it should already be matching a real OPP. >>> >>> Thoughts? >>> Quentin >> >> Can try that for a V2. That means em_pd_get_efficient_freq() would have to >> know about policy clamping (but I don't think that's an issue) > > Indeed, and I think we can even see this as an improvement as EAS will > now see policy clamps as well in compute_energy(). Are you sure that the 'policy' can be accessed from compute_energy()? It can be from schedutil freq switch path, but I'm not use about our feec().. For me this cpufreq_driver_resolve_freq sounds a bit out of this patch subject. Regards, Lukasz