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[141.239.149.160]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-1fbb6ab75besm18174215ad.148.2024.07.09.09.43.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jul 2024 09:43:07 -0700 (PDT) Sender: Tejun Heo Date: Tue, 9 Jul 2024 06:43:06 -1000 From: Tejun Heo To: Vincent Guittot Cc: rafael@kernel.org, viresh.kumar@linaro.org, linux-pm@vger.kernel.org, void@manifault.com, linux-kernel@vger.kernel.org, kernel-team@meta.com, mingo@redhat.com, peterz@infradead.org, David Vernet , "Rafael J . Wysocki" Subject: Re: [PATCH v2 2/2] sched_ext: Add cpuperf support Message-ID: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hello, On Tue, Jul 09, 2024 at 03:36:34PM +0200, Vincent Guittot wrote: > > I tried this and it's a bit problematic. Migrating out all the tasks do > > bring the numbers pretty close to zero but the math doesn't work out exactly > > and it often leaves 1 in the averages. While the fair class is in use, they > > hmm interesting, such remaining small value could be expected for > load_avg but not with util_avg which is normally a direct propagation. > Do you have a sequence in particular ? Oh, I thought it was a byproduct of decay calculations not exactly matching up between the sum and the components but I haven't really checked. It's really easy to reproduce. Just boot a kernel with sched_ext enabled (with some instrumentations added to monitor the util calculation), run some stress workload to be sure and run a sched_ext scheduler (make -C tools/sched_ext && tools/sched_ext/build/bin/scx_simple). Thanks. -- tejun