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[71.255.246.27]) by smtp.gmail.com with ESMTPSA id x6sm2391010qkh.20.2020.01.11.07.04.37 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 11 Jan 2020 07:04:37 -0800 (PST) Subject: Re: [Patch v6 0/7] Introduce Thermal Pressure To: Peter Zijlstra References: <1576123908-12105-1-git-send-email-thara.gopinath@linaro.org> <20191216145624.GU2844@hirez.programming.kicks-ass.net> Cc: mingo@redhat.com, ionela.voinescu@arm.com, vincent.guittot@linaro.org, rui.zhang@intel.com, qperret@google.com, daniel.lezcano@linaro.org, viresh.kumar@linaro.org, linux-kernel@vger.kernel.org, amit.kachhap@gmail.com, javi.merino@kernel.org, amit.kucheria@verdurent.com From: Thara Gopinath Message-ID: <5E19E404.1020601@linaro.org> Date: Sat, 11 Jan 2020 10:04:36 -0500 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: <20191216145624.GU2844@hirez.programming.kicks-ass.net> 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 12/16/2019 09:56 AM, Peter Zijlstra wrote: > On Wed, Dec 11, 2019 at 11:11:41PM -0500, Thara Gopinath wrote: >> Test Results >> >> Hackbench: 1 group , 30000 loops, 10 runs >> Result SD >> (Secs) (% of mean) >> No Thermal Pressure 14.03 2.69% >> Thermal Pressure PELT Algo. Decay : 32 ms 13.29 0.56% >> Thermal Pressure PELT Algo. Decay : 64 ms 12.57 1.56% >> Thermal Pressure PELT Algo. Decay : 128 ms 12.71 1.04% >> Thermal Pressure PELT Algo. Decay : 256 ms 12.29 1.42% >> Thermal Pressure PELT Algo. Decay : 512 ms 12.42 1.15% >> >> Dhrystone Run Time : 20 threads, 3000 MLOOPS >> Result SD >> (Secs) (% of mean) >> No Thermal Pressure 9.452 4.49% >> Thermal Pressure PELT Algo. Decay : 32 ms 8.793 5.30% >> Thermal Pressure PELT Algo. Decay : 64 ms 8.981 5.29% >> Thermal Pressure PELT Algo. Decay : 128 ms 8.647 6.62% >> Thermal Pressure PELT Algo. Decay : 256 ms 8.774 6.45% >> Thermal Pressure PELT Algo. Decay : 512 ms 8.603 5.41% > > What is the conclusion, if any from these results? Clearly thermal > pressuse seems to help, but what window? ISTR we default to 32ms, which > is a wash for drystone, but sub-optimal for hackbench. Hi Peter, Thanks for the reviews. IMHO, the conclusion is that thermal pressure is beneficial but the decay period to be used depends on the architecture and/or use-cases. Sticking to 32ms should give some improvement but it can be tuned depending on the system. > > > Anyway, the patches look more or less acceptible, just a bunch of nits, > the biggest being the fact that even if an architecture does not support > this there is still the code and runtime overhead. I am fixing this and sending out a v7. > -- Warm Regards Thara