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Documentation: Fix typos in energy model documentation

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Fix typos in documentation related to energy model management.

Signed-off-by: Patrick Little <plittle@gmail.com>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20260128-documentation-fix-grammar-v1-1-39238dc471f9@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Patrick Little 2026-01-28 16:33:11 -06:00 • committed by Rafael J. Wysocki
parent 63804fed14
commit e79eec6ca1
2 changed files with 11 additions and 11 deletions
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14
Documentation/power/energy-model.rst
View file

@ -14,8 +14,8 @@ subsystems willing to use that information to make energy-aware decisions.
The source of the information about the power consumed by devices can vary greatly
from one platform to another. These power costs can be estimated using
devicetree data in some cases. In others, the firmware will know better.
Alternatively, userspace might be best positioned. And so on. In order to avoid
each and every client subsystem to re-implement support for each and every
Alternatively, userspace might be best positioned. In order to avoid
having each and every client subsystem re-implement support for each and every
possible source of information on its own, the EM framework intervenes as an
abstraction layer which standardizes the format of power cost tables in the
kernel, hence enabling to avoid redundant work.
@ -32,7 +32,7 @@ be found in the Intelligent Power Allocation in
Documentation/driver-api/thermal/power_allocator.rst.
Kernel subsystems might implement automatic detection to check whether EM
registered devices have inconsistent scale (based on EM internal flag).
Important thing to keep in mind is that when the power values are expressed in
An important thing to keep in mind is that when the power values are expressed in
an 'abstract scale' deriving real energy in micro-Joules would not be possible.
The figure below depicts an example of drivers (Arm-specific here, but the
@ -82,7 +82,7 @@ using kref mechanism. The device driver which provided the new EM at runtime,
should call EM API to free it safely when it's no longer needed. The EM
framework will handle the clean-up when it's possible.
The kernel code which want to modify the EM values is protected from concurrent
The kernel code which wants to modify the EM values is protected from concurrent
access using a mutex. Therefore, the device driver code must run in sleeping
context when it tries to modify the EM.
@ -113,7 +113,7 @@ Registration of 'advanced' EM
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'advanced' EM gets its name due to the fact that the driver is allowed
to provide more precised power model. It's not limited to some implemented math
to provide a more precise power model. It's not limited to some implemented math
formula in the framework (like it is in 'simple' EM case). It can better reflect
the real power measurements performed for each performance state. Thus, this
registration method should be preferred in case considering EM static power
@ -172,7 +172,7 @@ Registration of 'simple' EM
~~~~~~~~~~~~~~~~~~~~~~~~~~~
The 'simple' EM is registered using the framework helper function
cpufreq_register_em_with_opp(). It implements a power model which is tight to
cpufreq_register_em_with_opp(). It implements a power model which is tied to a
math formula::
Power = C * V^2 * f
@ -251,7 +251,7 @@ It returns the 'struct em_perf_state' pointer which is an array of performance
states in ascending order.
This function must be called in the RCU read lock section (after the
rcu_read_lock()). When the EM table is not needed anymore there is a need to
call rcu_real_unlock(). In this way the EM safely uses the RCU read section
call rcu_read_unlock(). In this way the EM safely uses the RCU read section
and protects the users. It also allows the EM framework to manage the memory
and free it. More details how to use it can be found in Section 3.2 in the
example driver.

8
Documentation/scheduler/sched-energy.rst
View file

@ -244,7 +244,7 @@ Example 2.
From these calculations, the Case 1 has the lowest total energy. So CPU 1
is be the best candidate from an energy-efficiency standpoint.
is the best candidate from an energy-efficiency standpoint.
Big CPUs are generally more power hungry than the little ones and are thus used
mainly when a task doesn't fit the littles. However, little CPUs aren't always
@ -252,7 +252,7 @@ necessarily more energy-efficient than big CPUs. For some systems, the high OPPs
of the little CPUs can be less energy-efficient than the lowest OPPs of the
bigs, for example. So, if the little CPUs happen to have enough utilization at
a specific point in time, a small task waking up at that moment could be better
of executing on the big side in order to save energy, even though it would fit
off executing on the big side in order to save energy, even though it would fit
on the little side.
And even in the case where all OPPs of the big CPUs are less energy-efficient
@ -285,7 +285,7 @@ much that can be done by the scheduler to save energy without severely harming
throughput. In order to avoid hurting performance with EAS, CPUs are flagged as
'over-utilized' as soon as they are used at more than 80% of their compute
capacity. As long as no CPUs are over-utilized in a root domain, load balancing
is disabled and EAS overridess the wake-up balancing code. EAS is likely to load
is disabled and EAS overrides the wake-up balancing code. EAS is likely to load
the most energy efficient CPUs of the system more than the others if that can be
done without harming throughput. So, the load-balancer is disabled to prevent
it from breaking the energy-efficient task placement found by EAS. It is safe to
@ -385,7 +385,7 @@ Using EAS with any other governor than schedutil is not supported.
6.5 Scale-invariant utilization signals
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In order to make accurate prediction across CPUs and for all performance
In order to make accurate predictions across CPUs and for all performance
states, EAS needs frequency-invariant and CPU-invariant PELT signals. These can
be obtained using the architecture-defined arch_scale{cpu,freq}_capacity()
callbacks.