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sched/doc: Factorize bits between sched-energy.rst & sched-capacity.rst 

Documentation/scheduler/sched-capacity.rst ought to be the canonical place
to blabber about SD_ASYM_CPUCAPACITY, so remove its explanation from
sched-energy.rst and point to sched-capacity.rst instead.

Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200731192016.7484-4-valentin.schneider@arm.com
zero-sugar-mainline-defconfig
Valentin Schneider 2020-07-31 20:20:16 +01:00 committed by Ingo Molnar
parent 65065fd70b
commit 949bcb8135
1 changed files with 2 additions and 10 deletions
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Documentation/scheduler/sched-energy.rst
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@ -331,16 +331,8 @@ asymmetric CPU topologies for now. This requirement is checked at run-time by
looking for the presence of the SD_ASYM_CPUCAPACITY flag when the scheduling
domains are built.
The flag is set/cleared automatically by the scheduler topology code whenever
there are CPUs with different capacities in a root domain. The capacities of
CPUs are provided by arch-specific code through the arch_scale_cpu_capacity()
callback. As an example, arm and arm64 share an implementation of this callback
which uses a combination of CPUFreq data and device-tree bindings to compute the
capacity of CPUs (see drivers/base/arch_topology.c for more details).
So, in order to use EAS on your platform your architecture must implement the
arch_scale_cpu_capacity() callback, and some of the CPUs must have a lower
capacity than others.
See Documentation/sched/sched-capacity.rst for requirements to be met for this
flag to be set in the sched_domain hierarchy.
Please note that EAS is not fundamentally incompatible with SMP, but no
significant savings on SMP platforms have been observed yet. This restriction