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[71.255.245.97]) by smtp.gmail.com with ESMTPSA id m18sm37360330qki.64.2019.04.17.10.28.20 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 17 Apr 2019 10:28:21 -0700 (PDT) Subject: Re: [PATCH V2 0/3] Introduce Thermal Pressure To: Ingo Molnar References: <1555443521-579-1-git-send-email-thara.gopinath@linaro.org> <20190417053626.GA47282@gmail.com> <20190417055514.GA27400@gmail.com> 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 From: Thara Gopinath Message-ID: <5CB76233.9080508@linaro.org> Date: Wed, 17 Apr 2019 13:28:19 -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: <20190417055514.GA27400@gmail.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/17/2019 01:55 AM, Ingo Molnar wrote: > > * 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! >> >> 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 > > So what I forgot to say is that IMO your results show robust improvements > over the vanilla kernel of around 5%, with a relatively straightforward > thermal pressure metric. So I suspect we could do something like this, if > there was a bit more measurements done to get the best decay period > established - the 125-250-500 msecs results seem a bit coarse and not > entirely unambiguous. To give you the background, I started with decay period of 500 ms. No other reason except the previous version of rt-pressure that existed in the scheduler employed a 500 ms decay period. Then the idea was to decrease the decay period by half and see what happens and so on. But I agree, that it is a bit coarse. I will probably get around to implementing some of your suggestions to capture more granular results in the next few weeks. > > In terms of stddev: the perf stat --pre hook could be used to add a dummy > benchmark run, to heat up the test system, to get more reliable, less > noisy numbers? > > BTW., that big improvement in hackbench results to 7.52 at 250 msecs, is > that real, or a fluke perhaps? For me, it is an anomaly. Having said that, I did rerun the tests with this configuration at least twice(if not more) and the results were similar. It is an anomaly because I have no explanation as to why there is so much improvement at the 250 ms decay period. > > Thanks, > > Ingo > -- Regards Thara