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Wysocki" , Viresh Kumar , Juri Lelli , Steven Rostedt , John Stultz , Dietmar Eggemann , Tim Chen , "Chen, Yu C" , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH v2 09/13] sched/qos: Add rampup multiplier QoS Date: Thu, 18 Jun 2026 16:30:05 +0800 Message-ID: <20260618083005.1432882-1-soolaugust@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260504020003.71306-10-qyousef@layalina.io> References: <20260504020003.71306-1-qyousef@layalina.io> <20260504020003.71306-10-qyousef@layalina.io> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Qais, I did a bit of testing on an Android device running 6.18.20-android17 with UTIL_EST and UTIL_EST_RAMPUP_ZERO enabled, and sched_qos_default_rampup_multiplier=0. At the scheduler level, the behaviour looks as expected. With rampup_multiplier=0, the worker's se.avg.util_est stayed at 0 in my runs. With rampup_multiplier=4, util_est became non-zero immediately in the high phase and reached ~1023. For end-to-end behaviour, I could not get a useful signal from longer steady CPU-bound phases. q0 tends to catch up via util_avg quickly, and the result is very sensitive to the frequency state at the start of the high phase. The clearest signal I saw was with a synthetic low-periodic -> short-burst native workload: low: periodic short work + sleep high: 5 CPU-bound cycles, no sleep Each q0/q4 case was gated to start from <= 940800 kHz on CPU4, and the worker set and verified the QoS value in the worker thread. In that setup, q4 was faster at the 5th high-cycle in 7/8 paired runs. The larger wins also matched q4 reaching a higher sampled CPU frequency during the burst, e.g. rep3: q0 691200 -> q4 1344000, c5 delta -41.9 ms rep5: q0 691200 -> q4 3398400, c5 delta -79.2 ms rep6: q0 691200 -> q4 1344000, c5 delta -91.9 ms The main negative case was consistent with the sampled frequency state too: rep1: q0 2083200 -> q4 816000, c5 delta +34.1 ms So this is only a synthetic transition-workload data point, but it does look consistent with the intended periodic-to-busy transition case. I would not interpret it as a general app benchmark result. No Tested-by tag from me for now, since this is not broad performance validation. Thanks, Zhidao