CPU load halfed after PR #40784

[alexsven]

Describe the bug
I noticed that the idle thread in simple samples like blinky is showing 49% cpu load. When checking out the commit just before the PR it shows 99% (as it should).
(#40784)

I've tested blinky for both nRF52840 and nRF5340, both show 49% CPU load for idle after PR, and 99% before the PR.

This PR was submitted by @peter-mitsis

[peter-mitsis]

Investigating ....

[peter-mitsis]

Alex,
What steps are you using to reproduce the problem? I ask because I am currently having difficulties just trying to build the blinky sample for the specified boards.

I've been trying to use ...
west build -p -b ./samples/basic/blinky
... to just get a basic build of the sample project but it is giving me Kconfig build errors, for every board name that contains nrf52840 that I have tried so far. At this point, I am assuming that either I have been picking the wrong board, and/or I have a knowledge gap.

[nashif]

west build -b nrf52840dk_nrf52811 ./samples/basic/blinky works fine...

[alexsven]

I used
west build -b nrf52840dk_nrf52840
and
west build -b nrf5340dk_nrf5340_cpuapp
depending on the board of course

[nordic-krch]

I am able to reproduce it on qemu_86 and qemu_86_64.
For reference, commit before the break: 0bd3d46.
Application i used: 36c210e

Prints 0.0% on 0bd3d46 and

Hello World! qemu_x86_64
load: 57.4%
load: 60.1%
load: 61.6%
load: 62.6%
load: 100.0%

on lastest.

[peter-mitsis]

I'm able to duplicate it now--also on qemu_x86.

[peter-mitsis]

I found at least one issue related to the updating of the system's thread_runtime_stats.

• The total cycles (non-idle) is including the number of idle cycles.

Consequently, the system's execution cycles (sum of total_cycles and idle cycles) ultimately includes the idle cycles twice.