What causes the CPU processing speed to slow down after OpenThread is enabled?

[Joyop]

Hi,

I found that runing a piece of code costs 490.21 us when OpenThread is disabled.  

However, after OpenThread is enabled, the time changed to 746.3 us as shown in the figure below:

Is this caused by the CPU usage of OpenThread?  If so what is the OpenThread protocol stack doing(triggering an IRQ?)?  Is there a way to reduce this impact?

The prj.conf is as follows:

#########
# Basic #
###################################################
CONFIG_GPIO=y

# Enable DK LED and Buttons library
CONFIG_DK_LIBRARY=y

# This example requires more workqueue stack
CONFIG_SYSTEM_WORKQUEUE_STACK_SIZE=2048

# Config logger
CONFIG_LOG=y
CONFIG_LOG_DEFAULT_LEVEL=3
CONFIG_LOG_BACKEND_UART=y
CONFIG_LOG_BACKEND_RTT=n
CONFIG_LOG_BACKEND_RTT_MODE_DROP=y
CONFIG_LOG_MODE_OVERFLOW=y
CONFIG_LOG_PRINTK=y
CONFIG_LOG_PRINTK_MAX_STRING_LENGTH=256
CONFIG_LOG_BUFFER_SIZE=4096
CONFIG_LOG_BACKEND_RTT_MESSAGE_SIZE=256
CONFIG_LOG_STRDUP_BUF_COUNT=64
CONFIG_LOG_STRDUP_MAX_STRING=64
CONFIG_LOG_BACKEND_SHOW_COLOR=n
CONFIG_LOG_BACKEND_FORMAT_TIMESTAMP=y

CONFIG_CONSOLE=y
CONFIG_USE_SEGGER_RTT=n
CONFIG_SEGGER_RTT_BUFFER_SIZE_UP=4096
CONFIG_RTT_CONSOLE=n
CONFIG_UART_CONSOLE=y

CONFIG_NRFX_SPIM3=y

CONFIG_NEWLIB_LIBC=y

CONFIG_EVENTS=y
###################################################


###############
# Open Thread #
###################################################
# Enable OpenThread features set
CONFIG_OPENTHREAD_NORDIC_LIBRARY_MASTER=y

CONFIG_NET_L2_OPENTHREAD=y

# Generic networking options
CONFIG_NETWORKING=y

CONFIG_ASSERT=y
CONFIG_ASSERT_NO_COND_INFO=y
CONFIG_MBEDTLS_SHA1_C=n
CONFIG_FPU=y
###################################################

Platform: Windows 10

NCS version: 1.9.1

Boards: nrf52840dk_nrf52840

IDE: SEGGER Embedded Studio（SES）

Looking forward to your reply.

Best wishes,

Joyop

[Charlie]

Hi Yao,

Thanks for your inquiry with us. Here are my opinions:

Is this caused by the CPU usage of OpenThread? 

I believe this is the cause. Just like a PC OS, your application logic will slow down when the CPU load is high. Zephyr Project provides CPU load measurement — nRF Connect SDK 1.9.1 documentation (nordicsemi.com) to track CPU load.

If so what is the OpenThread protocol stack doing(triggering an IRQ?)?  Is there a way to reduce this impact?

Hard to explain in a few words, you can find OT source codes from openthread/openthread: OpenThread released by Google is an open-source implementation of the Thread networking protocol (github.com).. You can also enable the OT log system to see what happens on its stack in real-time. but this will cost more CPU resources. I suggest you disable the log system to see if there is any improvement.

I am not a Zephyr OS expert. Zephyr Project | Contact Us Discord channel(discord.com/.../884102400149966930) may be a good place for a deeper discussion. I can invite you if you need more help.

Best regards,

Charlie

[Joyop]

Hi Charlie,

Thanks for your reply, I'm going to use CPU load measurement later to track CPU load.

Besides, please invite me into that channel and I'll see if it helps.

Best wishes,

Joyop