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[82.212.34.85]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45da15a6454sm14762033f8f.34.2026.05.15.06.57.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 06:57:40 -0700 (PDT) Date: Fri, 15 May 2026 15:57:40 +0200 Message-ID: <318a4aaf404b66f7a04ed4d4a18d228a.tomge68@gmail.com> From: Tom Gebhardt To: Christian Loehle Cc: Qais Yousef , linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , Vincent Guittot Subject: Re: [PATCH v2 00/13] sched/fair/schedutil: Better manage system response time In-Reply-To: <28c59186-4ba0-44f4-b5b8-42f6f73cd3e6@arm.com> References: <20260504020003.71306-1-qyousef@layalina.io> <20260515014250.tueinbuk7ldttdop@airbuntu> <32dea9123588227a02971341b22e84d3.tomge68@gmail.com> <28c59186-4ba0-44f4-b5b8-42f6f73cd3e6@arm.com> Content-Type: text/plain; charset=UTF-8 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Hi Christian, Good point -- I ran additional tests with `performance` and `ondemand` governors side by side on the same kernel (7.0.0 + ttwu + patch 12 only): Clock Governor pipe bogo ops/s -------- ------------ ---------------- 2400 MHz performance 2 095 187 2400 MHz ondemand 2 093 221 2800 MHz performance 2 415 817 2800 MHz ondemand 2 415 617 The difference between governors is <0.1% -- well within noise. So you are right: the effect is not cpufreq-related. Whatever patch 12 changes, it affects the scheduler path directly, not through frequency selection. I also applied Vincent's fix [1] and benchmarked it: Kernel Clock pipe bogo ops/s Δ vs. 6.6.78 ---------------------- -------- ---------------- ------------ 6.6.78 2400 MHz 2 129 330 ±0% 6.6.78 2800 MHz 2 487 746 ±0% 7.0 + ttwu + patch 12 2400 MHz 2 093 221 −1.7% 7.0 + ttwu + patch 12 2800 MHz 2 415 617 −2.9% 7.0 + ttwu + Vincent 2400 MHz 2 077 526 −2.4% 7.0 + ttwu + Vincent 2800 MHz 2 458 151 −1.2% Vincent's fix gets very close to 6.6 at 2800 MHz (−1.2%) and is similar to patch 12 at 2400 MHz. Both are a large improvement over vanilla 7.0+ttwu (−22% at 2800 MHz) and plain 7.0 stock (−26% at 2800 MHz). Note: [1] applied with a manual context fixup for the DELAY_DEQUEUE hunk -- the rpi-7.0.y tree's dequeue_entity() differs slightly from mainline in that block (no update_entity_lag() call inside the DELAY_DEQUEUE early-return). The semantic intent of the hunk was preserved. [1] https://lore.kernel.org/lkml/agRyoe1wHyZ-vMk9@vingu-cube/ Thanks for catching that and for offering to reproduce it. Tom