CPU percentage inside a docker container with cgroup v2

Question

I've been using this great Golang library to collect CPU percentage of the container (not the host like top command retrieves) but the repo seems to be inactive and can only collect cgroup v1 cpu percentage. https://github.com/HobbyBear/cmetric

For cgroup v2, I managed to calculate the percent usage for memory but I cannot get the CPU percentage correct.

Memory percentage for cgroup v2:

work out if cgroup v2 is used - below should equal cgroup2fs

stat -fc %T /sys/fs/cgroup/

Divide the current memory by the max memory. Note the memory limit in docker needs to be set.

cat /sys/fs/cgroup/memory.max

cat /sys/fs/cgroup/memory.current

Any advice on how to calculate the CPU percentage would be appreciated. :)

user_725021 · Answer

If I understand correctly the code in https://github.com/systemd/systemd-stable/blob/516108f273888df3dcfa4f42b140252a285a2288/src/cgtop/cgtop.c#L423 the percentage is computed with the derivative of CPU usage.

So, I am as sad as you: nothing gives you the CPU fraction or percentage used easily. I assumed it was a basic requirements for CPU accounting, but maybe this is a non goal for cgroups v2.

I wasn't able to find anything on this after hours of search. Except for systemd-cgtop

CPU percentage inside a docker container with cgroup v2

1 Answers