Process “ubd” high CPU usage

Question

I noticed my MBP got really slow, which must be strange with SSD and 8GB of RAM.

So I opened the Activity Monitor to discover a process called ubd keeps its CPU usage very high, about 120% most of the time:

I found a thread that discusses the issue but it is related to having hundreds of iCloud certificates in the keychain, which I don't.

How do I go on with diagnosing the issue?

Answer 1

By observing log messages in ~/Library/Logs/Ubiquity/<my username>/, I realized that Ubiquity (iCloud process) kept trying to create a file in a folder that doesn't exist:

I opened up the Terminal and created this directory and its parent directories up to .ubd:

cd ~/Library/Mobile\ Documents/
sudo mkdir .ubd && cd .ubd
sudo mkdir peer-E2B13E4F-56F7-C79B-1621-E30738B638FE-v23 && cd peer-E2B13E4F-56F7-C79B-1621-E30738B638FE-v23
sudo mkdir ftr

Then I changed the newly created directories' owner from root to myself:

cd ../..
sudo chown -R <my username> .ubd/ 

The fan turned silent instantly.