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[71.255.246.27]) by smtp.gmail.com with ESMTPSA id m5sm1544807qtp.97.2019.10.31.09.03.08 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 31 Oct 2019 09:03:09 -0700 (PDT) Subject: Re: [Patch v4 4/6] sched/fair: update cpu_capcity to reflect thermal pressure To: Qais Yousef , Peter Zijlstra References: <1571776465-29763-1-git-send-email-thara.gopinath@linaro.org> <1571776465-29763-5-git-send-email-thara.gopinath@linaro.org> <20191023122252.dz7obopab6iizy4s@e107158-lin.cambridge.arm.com> <20191028153010.GE4097@hirez.programming.kicks-ass.net> <20191031105342.b3sl5xhysldfla3g@e107158-lin.cambridge.arm.com> Cc: mingo@redhat.com, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, edubezval@gmail.com, qperret@google.com, linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, daniel.lezcano@linaro.org From: Thara Gopinath Message-ID: <5DBB05BC.40502@linaro.org> Date: Thu, 31 Oct 2019 12:03:08 -0400 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1 MIME-Version: 1.0 In-Reply-To: <20191031105342.b3sl5xhysldfla3g@e107158-lin.cambridge.arm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/31/2019 06:53 AM, Qais Yousef wrote: > On 10/28/19 16:30, Peter Zijlstra wrote: >> On Wed, Oct 23, 2019 at 01:28:40PM +0100, Qais Yousef wrote: >>> On 10/22/19 16:34, Thara Gopinath wrote: >>>> cpu_capacity relflects the maximum available capacity of a cpu. Thermal >>>> pressure on a cpu means this maximum available capacity is reduced. This >>>> patch reduces the average thermal pressure for a cpu from its maximum >>>> available capacity so that cpu_capacity reflects the actual >>>> available capacity. >>>> >>>> Signed-off-by: Thara Gopinath >>>> --- >>>> kernel/sched/fair.c | 1 + >>>> 1 file changed, 1 insertion(+) >>>> >>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >>>> index 4f9c2cb..be3e802 100644 >>>> --- a/kernel/sched/fair.c >>>> +++ b/kernel/sched/fair.c >>>> @@ -7727,6 +7727,7 @@ static unsigned long scale_rt_capacity(struct sched_domain *sd, int cpu) >>>> >>>> used = READ_ONCE(rq->avg_rt.util_avg); >>>> used += READ_ONCE(rq->avg_dl.util_avg); >>>> + used += READ_ONCE(rq->avg_thermal.load_avg); >>> >>> Maybe a naive question - but can we add util_avg with load_avg without >>> a conversion? I thought the 2 signals have different properties. >> >> Changelog of patch #1 explains, it's in that dense blob of text. >> >> But yes, you're quite right that that wants a comment here. > > Thanks for the pointer! A comment would be nice indeed. > > To make sure I got this correctly - it's because avg_thermal.load_avg > represents delta_capacity which is already a 'converted' form of load. So this > makes avg_thermal.load_avg a util_avg really. Correct? Hello Quais, Sorry for not replying to your earlier email. Thanks for the review. So if you look at the code, util_sum in calculated as a binary signal converted into capacity. Check out the the below snippet from accumulate_sum if (load) sa->load_sum += load * contrib; if (runnable) sa->runnable_load_sum += runnable * contrib; if (running) sa->util_sum += contrib << SCHED_CAPACITY_SHIFT; So the actual delta for the thermal pressure will never be considered if util_avg is used. I will update this patch with relevant comment. -- Warm Regards Thara