Today I upgraded my system to macOS Catalina 10.15 and found that the disk would heat up and the fan would start spinning loudly after using it for a while. Even if all applications were closed, this issue still occurred, and I suspected that the system was doing something in the background.
I directly opened the system’s built-in Activity Monitor monitoring tool and found that a process called “photoanalysisd” was running in the background, causing the CPU usage to soar to 40% to 50%.
This process is mainly used for analyzing the photos on the computer, but it is unclear exactly what it is doing (intelligence comes at a cost), so I stopped it immediately.
launchctl stop com.apple.photoanalysisd
launchctl unload -w /System/Library/LaunchAgents/com.apple.photoanalysisd.plist
The CPU usage immediately went down and the fan gradually stopped, everything returned to normal again.