linux-stable.git/include/linux/energy_model.h, branch v6.9.2 Linux kernel stable tree PM: EM: fix wrong utilization estimation in em_cpu_energy() 2024-04-04T17:27:53+00:00 Vincent Guittot vincent.guittot@linaro.org 2024-04-04T10:42:00+00:00 8130b05c559d1aa83d0c8971b422ba0da18ef24a Commit 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division") has added back map_util_perf() in em_cpu_energy() computation which has been removed with the rework of scheduler/cpufreq interface. This is wrong because sugov_effective_cpu_perf() already takes care of mapping the utilization to a performance level. Fixes: 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division") Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Reviewed-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
Commit 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division")
has added back map_util_perf() in em_cpu_energy() computation which has
been removed with the rework of scheduler/cpufreq interface.
This is wrong because sugov_effective_cpu_perf() already takes care of
mapping the utilization to a performance level.

Fixes: 1b600da51073 ("PM: EM: Optimize em_cpu_energy() and remove division")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Add em_dev_compute_costs() 2024-02-08T14:00:32+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:56+00:00 22ea02848c07d1cbd15a5f442138ca429866300d The device drivers can modify EM at runtime by providing a new EM table. The EM is used by the EAS and the em_perf_state::cost stores pre-calculated value to avoid overhead. This patch provides the API for device drivers to calculate the cost values properly (and not duplicate the same code). Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The device drivers can modify EM at runtime by providing a new EM table.
The EM is used by the EAS and the em_perf_state::cost stores
pre-calculated value to avoid overhead. This patch provides the API for
device drivers to calculate the cost values properly (and not duplicate
the same code).

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Remove old table 2024-02-08T14:00:32+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:55+00:00 24e9fb635df2790eccb0e95ff65c6dee7a97fcb7 Remove the old EM table which wasn't able to modify the data. Clean the unneeded function and refactor the code a bit. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
Remove the old EM table which wasn't able to modify the data. Clean the
unneeded function and refactor the code a bit.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Optimize em_cpu_energy() and remove division 2024-02-08T14:00:31+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:49+00:00 1b600da510735a0f92c8b4140a7e2cb037a6a6c3 The Energy Model (EM) can be modified at runtime which brings new possibilities. The em_cpu_energy() is called by the Energy Aware Scheduler (EAS) in its hot path. The energy calculation uses power value for a given performance state (ps) and the CPU busy time as percentage for that given frequency. It is possible to avoid the division by 'scale_cpu' at runtime, because EM is updated whenever new max capacity CPU is set in the system. Use that feature and do the needed division during the calculation of the coefficient 'ps->cost'. That enhanced 'ps->cost' value can be then just multiplied simply by utilization: pd_nrg = ps->cost * \Sum cpu_util to get the needed energy for whole Performance Domain (PD). With this optimization and earlier removal of map_util_freq(), the em_cpu_energy() should run faster on the Big CPU by 1.43x and on the Little CPU by 1.69x (RockPi 4B board). Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The Energy Model (EM) can be modified at runtime which brings new
possibilities. The em_cpu_energy() is called by the Energy Aware Scheduler
(EAS) in its hot path. The energy calculation uses power value for
a given performance state (ps) and the CPU busy time as percentage for that
given frequency.

It is possible to avoid the division by 'scale_cpu' at runtime, because
EM is updated whenever new max capacity CPU is set in the system.

Use that feature and do the needed division during the calculation of the
coefficient 'ps->cost'. That enhanced 'ps->cost' value can be then just
multiplied simply by utilization:

pd_nrg = ps->cost * \Sum cpu_util

to get the needed energy for whole Performance Domain (PD).

With this optimization and earlier removal of map_util_freq(), the
em_cpu_energy() should run faster on the Big CPU by 1.43x and on the Little
CPU by 1.69x (RockPi 4B board).

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Add performance field to struct em_perf_state and optimize 2024-02-08T14:00:31+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:47+00:00 5a367f7b7014af86bd1ac0865a42db55187dbd3c The performance doesn't scale linearly with the frequency. Also, it may be different in different workloads. Some CPUs are designed to be particularly good at some applications e.g. images or video processing and other CPUs in different. When those different types of CPUs are combined in one SoC they should be properly modeled to get max of the HW in Energy Aware Scheduler (EAS). The Energy Model (EM) provides the power vs. performance curves to the EAS, but assumes the CPUs capacity is fixed and scales linearly with the frequency. This patch allows to adjust the curve on the 'performance' axis as well. Code speed optimization: Removing map_util_freq() allows to avoid one division and one multiplication operations from the EAS hot code path. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The performance doesn't scale linearly with the frequency. Also, it may
be different in different workloads. Some CPUs are designed to be
particularly good at some applications e.g. images or video processing
and other CPUs in different. When those different types of CPUs are
combined in one SoC they should be properly modeled to get max of the HW
in Energy Aware Scheduler (EAS). The Energy Model (EM) provides the
power vs. performance curves to the EAS, but assumes the CPUs capacity
is fixed and scales linearly with the frequency. This patch allows to
adjust the curve on the 'performance' axis as well.

Code speed optimization:
Removing map_util_freq() allows to avoid one division and one
multiplication operations from the EAS hot code path.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Add em_perf_state_from_pd() to get performance states table 2024-02-08T14:00:31+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:46+00:00 ee1a19873ce1234a3c2e6f84af3624fc73bfbd9c Introduce a wrapper to get the performance states table of the performance domain. The function should be called within the RCU read critical section. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
Introduce a wrapper to get the performance states table of the performance
domain. The function should be called within the RCU read critical
section.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Introduce em_dev_update_perf_domain() for EM updates 2024-02-08T14:00:30+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:45+00:00 977230d5d50314f9920d3ee6348773d8babbfb58 Add API function em_dev_update_perf_domain() which allows the EM to be changed safely. Concurrent updaters are serialized with a mutex and the removal of memory that will not be used any more is carried out with the help of RCU. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
Add API function em_dev_update_perf_domain() which allows the EM to be
changed safely.

Concurrent updaters are serialized with a mutex and the removal of memory
that will not be used any more is carried out with the help of RCU.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Add functions for memory allocations for new EM tables 2024-02-08T14:00:30+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:44+00:00 ffcf9bce7af02a21fb73738999de1e3d4fde5aca The runtime modified EM table can be provided from drivers. Create mechanism which allows safely allocate and free the table for device drivers. The same table can be used by the EAS in task scheduler code paths, so make sure the memory is not freed when the device driver module is unloaded. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The runtime modified EM table can be provided from drivers. Create
mechanism which allows safely allocate and free the table for device
drivers. The same table can be used by the EAS in task scheduler code
paths, so make sure the memory is not freed when the device driver module
is unloaded.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Use runtime modified EM for CPUs energy estimation in EAS 2024-02-08T14:00:28+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:43+00:00 aa11a7ebfd5d698f541641922beede1cb474bf70 The new Energy Model (EM) supports runtime modification of the performance state table to better model the power used by the SoC. Use this new feature to improve energy estimation and therefore task placement in Energy Aware Scheduler (EAS). Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The new Energy Model (EM) supports runtime modification of the performance
state table to better model the power used by the SoC. Use this new
feature to improve energy estimation and therefore task placement in
Energy Aware Scheduler (EAS).

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
PM: EM: Introduce runtime modifiable table 2024-02-08T14:00:27+00:00 Lukasz Luba lukasz.luba@arm.com 2024-02-08T11:55:42+00:00 ca0fc871f16f4bef746b5ba814b67afb59119700 The new runtime table can be populated with a new power data to better reflect the actual efficiency of the device e.g. CPU. The power can vary over time e.g. due to the SoC temperature change. Higher temperature can increase power values. For longer running scenarios, such as game or camera, when also other devices are used (e.g. GPU, ISP) the CPU power can change. The new EM framework is able to addresses this issue and change the EM data at runtime safely. Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> 
The new runtime table can be populated with a new power data to better
reflect the actual efficiency of the device e.g. CPU. The power can vary
over time e.g. due to the SoC temperature change. Higher temperature can
increase power values. For longer running scenarios, such as game or
camera, when also other devices are used (e.g. GPU, ISP) the CPU power can
change. The new EM framework is able to addresses this issue and change
the EM data at runtime safely.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>