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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id w10sm39466529wrv.8.2019.04.17.11.29.34 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 17 Apr 2019 11:29:35 -0700 (PDT) Date: Wed, 17 Apr 2019 20:29:32 +0200 From: Ingo Molnar To: Thara Gopinath Cc: mingo@redhat.com, peterz@infradead.org, rui.zhang@intel.com, linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, viresh.kumar@linaro.org, javi.merino@kernel.org, edubezval@gmail.com, daniel.lezcano@linaro.org, vincent.guittot@linaro.org, nicolas.dechesne@linaro.org, bjorn.andersson@linaro.org, dietmar.eggemann@arm.com, Quentin Perret , "Rafael J. Wysocki" Subject: Re: [PATCH V2 0/3] Introduce Thermal Pressure Message-ID: <20190417182932.GB5140@gmail.com> References: <1555443521-579-1-git-send-email-thara.gopinath@linaro.org> <20190417053626.GA47282@gmail.com> <5CB75FD9.3070207@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5CB75FD9.3070207@linaro.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Thara Gopinath wrote: > > On 04/17/2019 01:36 AM, Ingo Molnar wrote: > > > > * Thara Gopinath wrote: > > > >> The test results below shows 3-5% improvement in performance when > >> using the third solution compared to the default system today where > >> scheduler is unware of cpu capacity limitations due to thermal events. > > > > The numbers look very promising! > > Hello Ingo, > Thank you for the review. > > > > I've rearranged the results to make the performance properties of the > > various approaches and parameters easier to see: > > > > (seconds, lower is better) > > > > Hackbench Aobench Dhrystone > > ========= ======= ========= > > Vanilla kernel (No Thermal Pressure) 10.21 141.58 1.14 > > Instantaneous thermal pressure 10.16 141.63 1.15 > > Thermal Pressure Averaging: > > - PELT fmwk 9.88 134.48 1.19 > > - non-PELT Algo. Decay : 500 ms 9.94 133.62 1.09 > > - non-PELT Algo. Decay : 250 ms 7.52 137.22 1.012 > > - non-PELT Algo. Decay : 125 ms 9.87 137.55 1.12 > > > > > > Firstly, a couple of questions about the numbers: > > > > 1) > > > > Is the 1.012 result for "non-PELT 250 msecs Dhrystone" really 1.012? > > You reported it as: > > > > non-PELT Algo. Decay : 250 ms 1.012 7.02% > > It is indeed 1.012. So, I ran the "non-PELT Algo 250 ms" benchmarks > multiple time because of the anomalies noticed. 1.012 is a formatting > error on my part when I copy pasted the results into a google sheet I am > maintaining to capture the test results. Sorry about the confusion. That's actually pretty good, because it suggests a 35% and 15% improvement over the vanilla kernel - which is very good for such CPU-bound workloads. Not that 5% is bad in itself - but 15% is better ;-) > Regarding the decay period, I agree that more testing can be done. I > like your suggestions below and I am going to try implementing them > sometime next week. Once I have some solid results, I will send them > out. Thanks! > My concern regarding getting hung up too much on decay period is that I > think it could vary from SoC to SoC depending on the type and number of > cores and thermal characteristics. So I was thinking eventually the > decay period should be configurable via a config option or by any other > means. Testing on different systems will definitely help and maybe I am > wrong and there is no much variation between systems. Absolutely, so I'd not be against keeping it a SCHED_DEBUG tunable or so, until there's a better understanding of how the physical properties of the SoC map to an ideal decay period. Assuming PeterZ & Rafael & Quentin doesn't hate the whole thermal load tracking approach. I suppose there's some connection of this to Energy Aware Scheduling? Or not ... Thanks, Ingo