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[71.163.245.5]) by smtp.gmail.com with ESMTPSA id s10sm134688qke.132.2021.11.17.09.01.04 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 17 Nov 2021 09:01:05 -0800 (PST) Subject: Re: [PATCH] base: arch_topology: Use policy->max to calculate freq_factor To: "Rafael J. Wysocki" , Lukasz Luba Cc: Sudeep Holla , Greg Kroah-Hartman , Bjorn Andersson , Linux Kernel Mailing List , linux-arm-msm References: <20211115201010.68567-1-thara.gopinath@linaro.org> <8f7397e3-4e92-c84d-9168-087967f4d683@arm.com> From: Thara Gopinath Message-ID: Date: Wed, 17 Nov 2021 12:01:04 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 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, On 11/17/21 7:49 AM, Rafael J. Wysocki wrote: > On Wed, Nov 17, 2021 at 11:46 AM Lukasz Luba wrote: >> >> Hi Rafael, >> >> On 11/16/21 7:05 PM, Rafael J. Wysocki wrote: >>> On Mon, Nov 15, 2021 at 9:10 PM Thara Gopinath >>> wrote: >>>> >>>> cpuinfo.max_freq can reflect boost frequency if enabled during boot. Since >>>> we don't consider boost frequencies while calculating cpu capacities, use >>>> policy->max to populate the freq_factor during boot up. >>> >>> I'm not sure about this. schedutil uses cpuinfo.max_freq as the max frequency. >> >> Agree it's tricky how we treat the boost frequencies and also combine >> them with thermal pressure. >> We probably would have consider these design bits: >> 1. Should thermal pressure include boost frequency? > > Well, I guess so. > > Running at a boost frequency certainly increases thermal pressure. > >> 2. Should max capacity 1024 be a boost frequency so scheduler >> would see it explicitly? > > That's what it is now if cpuinfo.max_freq is a boost frequency. > >> - if no, then schedutil could still request boost freq thanks to >> map_util_perf() where we add 25% to the util and then >> map_util_freq() would return a boost freq when util was > 1024 >> >> >> I can see in schedutil only one place when cpuinfo.max_freq is used: >> get_next_freq(). If the value stored in there is a boost, >> then don't we get a higher freq value for the same util? > > Yes. we do, which basically is my point. > > The schedutil's response is proportional to cpuinfo.max_freq and that > needs to be taken into account for the results to be consistent. So IIUC, cpuinfo.max_freq is always supposed to be the highest supported frequency of a cpu, irrespective of whether boost is enabled or not. Where as policy->max is the currently available maximum cpu frequency which can be equal to cpuinfo.max_freq or lower (depending on whether boost is enabled, whether there is a constraint on policy->max placed by thermal etc). So in this case isn't it better for schedutil to consider policy->max instead of cpuinfo.max ? Like you mentioned above same utilization will relate to different frequencies depending on the maximum frequency. > -- Warm Regards Thara (She/Her/Hers)