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[ Upstream commitad841e569f] When evaluating the CPU candidates in the perf domain (pd) containing the previously used CPU (prev_cpu), find_energy_efficient_cpu() evaluates the energy of the pd: - without the task (base_energy) - with the task placed on prev_cpu (if the task fits) - with the task placed on the CPU with the highest spare capacity, prev_cpu being excluded from this set If prev_cpu is already the CPU with the highest spare capacity, max_spare_cap_cpu will be the CPU with the second highest spare capacity. On an Arm64 Juno-r2, with a workload of 10 tasks at a 10% duty cycle, when prev_cpu and max_spare_cap_cpu are both valid candidates, prev_spare_cap > max_spare_cap at ~82%. Thus the energy of the pd when placing the task on max_spare_cap_cpu is computed with no possible positive outcome 82% most of the time. Do not consider max_spare_cap_cpu as a valid candidate if prev_spare_cap > max_spare_cap. Signed-off-by: Pierre Gondois <pierre.gondois@arm.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Link: https://lore.kernel.org/r/20221006081052.3862167-2-pierre.gondois@arm.com Stable-dep-of:e26fd28db8("sched/uclamp: Fix a uninitialized variable warnings") Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.