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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,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 2D319C433DB for ; Tue, 9 Mar 2021 10:02:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2C6E65257 for ; Tue, 9 Mar 2021 10:02:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229688AbhCIKBz (ORCPT ); Tue, 9 Mar 2021 05:01:55 -0500 Received: from foss.arm.com ([217.140.110.172]:50756 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229689AbhCIKBr (ORCPT ); Tue, 9 Mar 2021 05:01:47 -0500 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 85BD831B; Tue, 9 Mar 2021 02:01:46 -0800 (PST) Received: from [10.57.15.199] (unknown [10.57.15.199]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 79C6A3F71B; Tue, 9 Mar 2021 02:01:45 -0800 (PST) Subject: Re: [PATCH 5/5] powercap/drivers/dtpm: Scale the power with the load To: Daniel Lezcano Cc: rafael@kernel.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org References: <20210301212149.22877-1-daniel.lezcano@linaro.org> <20210301212149.22877-5-daniel.lezcano@linaro.org> From: Lukasz Luba Message-ID: Date: Tue, 9 Mar 2021 10:01:43 +0000 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: <20210301212149.22877-5-daniel.lezcano@linaro.org> 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 Daniel, I've started reviewing the series, please find some comments below. On 3/1/21 9:21 PM, Daniel Lezcano wrote: > Currently the power consumption is based on the current OPP power > assuming the entire performance domain is fully loaded. > > That gives very gross power estimation and we can do much better by > using the load to scale the power consumption. > > Use the utilization to normalize and scale the power usage over the > max possible power. > > Tested on a rock960 with 2 big CPUS, the power consumption estimation > conforms with the expected one. > > Before this change: > > ~$ ~/dhrystone -t 1 -l 10000& > ~$ cat /sys/devices/virtual/powercap/dtpm/dtpm:0/dtpm:0:1/constraint_0_max_power_uw > 2260000 > > After this change: > > ~$ ~/dhrystone -t 1 -l 10000& > ~$ cat /sys/devices/virtual/powercap/dtpm/dtpm:0/dtpm:0:1/constraint_0_max_power_uw > 1130000 > > ~$ ~/dhrystone -t 2 -l 10000& > ~$ cat /sys/devices/virtual/powercap/dtpm/dtpm:0/dtpm:0:1/constraint_0_max_power_uw > 2260000 > > Signed-off-by: Daniel Lezcano > --- > drivers/powercap/dtpm_cpu.c | 21 +++++++++++++++++---- > 1 file changed, 17 insertions(+), 4 deletions(-) > > diff --git a/drivers/powercap/dtpm_cpu.c b/drivers/powercap/dtpm_cpu.c > index e728ebd6d0ca..8379b96468ef 100644 > --- a/drivers/powercap/dtpm_cpu.c > +++ b/drivers/powercap/dtpm_cpu.c > @@ -68,27 +68,40 @@ static u64 set_pd_power_limit(struct dtpm *dtpm, u64 power_limit) > return power_limit; > } > > +static u64 scale_pd_power_uw(struct cpumask *cpus, u64 power) renamed 'cpus' into 'pd_mask', see below > +{ > + unsigned long max, util; > + int cpu, load = 0; IMHO 'int load' looks odd when used with 'util' and 'max'. I would put in the line above to have them all the same type and renamed to 'sum_util'. > + > + for_each_cpu(cpu, cpus) { I would avoid the temporary CPU mask in the get_pd_power_uw() with this modified loop: for_each_cpu_and(cpu, pd_mask, cpu_online_mask) { > + max = arch_scale_cpu_capacity(cpu); > + util = sched_cpu_util(cpu, max); > + load += ((util * 100) / max); Below you can find 3 optimizations. Since we are not in the hot path here, it's up to if you would like to use all/some of them or just ignore. 1st optimization. If we use 'load += (util << 10) / max' in the loop, then we could avoid div by 100 and use a right shift: (power * load) >> 10 2nd optimization. Since we use EM CPU mask, which span all CPUs with the same arch_scale_cpu_capacity(), you can avoid N divs inside the loop and do it once, below the loop. 3rd optimization. If we just simply add all 'util' into 'sum_util' (no mul or div in the loop), then we might just have simple macro #define CALC_POWER_USAGE(power, sum_util, max) \ (((power * (sum_util << 10)) / max) >> 10) > + } > + > + return (power * load) / 100; > +} > + > static u64 get_pd_power_uw(struct dtpm *dtpm) > { > struct dtpm_cpu *dtpm_cpu = to_dtpm_cpu(dtpm); > struct em_perf_domain *pd; > struct cpumask cpus; Since we don't need the 'nr_cpus' we also don't need the cpumask which occupy stack; Maybe use struct cpumask *pd_mask; then > unsigned long freq; > - int i, nr_cpus; > + int i; > > pd = em_cpu_get(dtpm_cpu->cpu); > freq = cpufreq_quick_get(dtpm_cpu->cpu); > > cpumask_and(&cpus, cpu_online_mask, to_cpumask(pd->cpus)); remove ^^^^^ and set pd_mask = em_span_cpus(pd); > - nr_cpus = cpumask_weight(&cpus); > > for (i = 0; i < pd->nr_perf_states; i++) { > > if (pd->table[i].frequency < freq) > continue; > > - return pd->table[i].power * > - MICROWATT_PER_MILLIWATT * nr_cpus; > + return scale_pd_power_uw(&cpus, pd->table[i].power * > + MICROWATT_PER_MILLIWATT); Instead of '&cpus' I would put 'pd_mask' and that should do the job. > } > > return 0; > Apart from that, the design idea with util looks good. Regards, Lukasz