Solution to kacpid high CPU usage Jan 8th 2020 Words: 191
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Locate the problem

I have observed that something on my laptop occasionally hog up one of my CPU core.

By list the processes, I believe the kacpid is responsible for this.

To find the culprit behind the process, watch -n "cat /proc/interrupts"

It is confirmed that the ACPI has some problem.
Now list the detail of acpi interrupts: for f in /sys/firmware/acpi/interrupts/*; do echo -ne "$f:\t\t" && cat $f; done

Found it! GPE 0x6F has obviously abnormal value.

Solution

First use a temporary solution to see if it solve the symptom. 

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sudo -s
echo "disable" > /sys/firmware/acpi/interrupts/gpe6F

The CPU usage drops to normal immediately.

But the above fix won’t be persist after reboot. You can add that command to a boot-up script, but it’s better to mask the interrupts use a kernel option. 

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sudo nano /etc/default/grub
# Add the option to the following line
GRUB_CMDLINE_LINUX_DEFAULT="acpi_mask_gpe=0x6F"
update-grub

Reboot.
Now verify the option has taken effect: cat /sys/firmware/acpi/interrupts/gpe6F

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# It should display masked
       0         enabled      masked

Done.