14fc6af67b
commit 44750f153699b6e4f851a399287e5c8df208d696 upstream.
While stressing EAS on my dragonboard RB3, I have noticed that LITTLE cores
where never selected as the most energy efficient CPU whatever the
utilization level of waking task.
energy model framework uses its cost field to estimate the energy with
the formula:
nrg = cost of the selected OPP * utilization / CPU's max capacity
which ends up selecting the CPU with lowest cost / max capacity ration
as long as the utilization fits in the OPP's capacity.
If we compare the cost of a little OPP with similar capacity of a big OPP
like :
OPP(kHz) OPP capacity cost max capacity cost/max capacity
LITTLE 1766400 407 351114 407 863
big 1056000 408 520267 1024 508
This can be interpreted as the LITTLE core consumes 70% more than big core
for the same compute capacity.
According to [1], LITTLE consumes 10% less than big core for Coremark
benchmark at those OPPs. If we consider that everything else stays
unchanged, the dynamic-power-coefficient of LITTLE core should be
only 53% of the current value: 290 * 53% = 154
Set the dynamic-power-coefficient of CPU0-3 to 154 to fix the energy model.
[1] https://github.com/kdrag0n/freqbench/tree/master/results/sdm845/main
Fixes: 0e0a8e35d725 ("arm64: dts: qcom: sdm845: correct dynamic power coefficients")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230106164618.1845281-1-vincent.guittot@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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.