How to check hardware usage (CPU, Memory, disk I/O) consumed by a process of a website?
Go to Tools & Settings > Process List (under Assistance and Troubleshooting).
Note: If Process List is not available, make sure that the Repair Kit Plesk Extension is installed and enabled.
Click Domains only to exclude system processes.
Turn on Auto-update of resource usage to track processes in real time.
Note: To sort the processes by CPU usage, Memory usage, Disk I/O (read), Disk I/O (write), click on the corresponding column.