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[77.199.4.181]) by smtp.gmail.com with ESMTPSA id d28sm25319430wrc.50.2020.06.23.09.47.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Jun 2020 09:47:34 -0700 (PDT) Date: Tue, 23 Jun 2020 18:47:33 +0200 From: Willy Wolff To: Chanwoo Choi , MyungJoo Ham , Kyungmin Park , Kukjin Kim , Krzysztof Kozlowski , linux-pm@vger.kernel.org, linux-samsung-soc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: brocken devfreq simple_ondemand for Odroid XU3/4? Message-ID: <20200623164733.qbhua7b6cg2umafj@macmini.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: linux-pm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org Hi everybody, Is DVFS for memory bus really working on Odroid XU3/4 board? Using a simple microbenchmark that is doing only memory accesses, memory DVFS seems to not working properly: The microbenchmark is doing pointer chasing by following index in an array. Indices in the array are set to follow a random pattern (cutting prefetcher), and forcing RAM access. git clone https://github.com/wwilly/benchmark.git \ && cd benchmark \ && source env.sh \ && ./bench_build.sh \ && bash source/scripts/test_dvfs_mem.sh Python 3, cmake and sudo rights are required. Results: DVFS CPU with performance governor mem_gov = simple_ondemand at 165000000 Hz in idle, should be bumped when the benchmark is running. - on the LITTLE cluster it takes 4.74308 s to run (683.004 c per memory access), - on the big cluster it takes 4.76556 s to run (980.343 c per moemory access). While forcing DVFS memory bus to use performance governor, mem_gov = performance at 825000000 Hz in idle, - on the LITTLE cluster it takes 1.1451 s to run (164.894 c per memory access), - on the big cluster it takes 1.18448 s to run (243.664 c per memory access). The kernel used is the last 5.7.5 stable with default exynos_defconfig. Cheers, Willy