This thread is a bad example for a post with a problem report.
It’s essentially lacking all of the information that anyone capable and willing to help would need at the very least to answer.
This is why there are no answers.
The used hardware is not mentioned. The used image is not named.
The old and the new OH version are not mentioned.
Neither the bindings used nor any other config details were given.
No proper description of the installation process.
No diagnostics whatsoever (to show ongoing I/O, ZRAM usage etc), no possibly relevant log entries. Screenshot instead of text.
RAM shortage is one of the prime reasons and depends on all of these inputs.
If you run a Pi 3 with just 1 GB of memory, you should not be using a 64 bit image.
But since high CPU load is a complex symptom with several potential causes and you want others to help you, you have to be helpful yourself first and provide comprehensive information upfront.
Please go read the official openHABian prerequisites and installation instructions, and check out the requirements on a proper forum post - notably #10 .
Then best practice is to create your own thread, and this time include all the requested information.