sched/topology: Consolidate and clean up access to a CPU's max compute capacity

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Remove the rq::cpu_capacity_orig field and use arch_scale_cpu_capacity()
instead.

The scheduler uses 3 methods to get access to a CPU's max compute capacity:

 - arch_scale_cpu_capacity(cpu) which is the default way to get a CPU's capacity.

 - cpu_capacity_orig field which is periodically updated with
   arch_scale_cpu_capacity().

 - capacity_orig_of(cpu) which encapsulates rq->cpu_capacity_orig.

There is no real need to save the value returned by arch_scale_cpu_capacity()
in struct rq. arch_scale_cpu_capacity() returns:

 - either a per_cpu variable.

 - or a const value for systems which have only one capacity.

Remove rq::cpu_capacity_orig and use arch_scale_cpu_capacity() everywhere.

No functional changes.

Some performance tests on Arm64:

  - small SMP device (hikey): no noticeable changes
  - HMP device (RB5):         hackbench shows minor improvement (1-2%)
  - large smp (thx2):         hackbench and tbench shows minor improvement (1%)

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://lore.kernel.org/r/20231009103621.374412-2-vincent.guittot@linaro.org

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This commit is contained in:

Vincent Guittot 2023-10-09 12:36:16 +02:00 • committed by Ingo Molnar

parent 089768dfeb

commit 7bc263840b

8 changed files with 25 additions and 29 deletions

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13

Documentation/scheduler/sched-capacity.rst

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2

kernel/sched/core.c

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2

kernel/sched/cpudeadline.c

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4

kernel/sched/deadline.c

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18

kernel/sched/fair.c

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2

kernel/sched/rt.c

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6

kernel/sched/sched.h

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7

kernel/sched/topology.c

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