http://docs-legacy.fortinet.com/fadc/4-1-0/index.html#page/FortiADC_Handbook/looking_for_system_intensive_processes.html
Killing system-intensive processes
Use
the CLI to view a list of the most system-intensive processes. This may
show processes that are consuming resources unusually. For example:
diagnose system top 10
The
above command generates a report of processes every 10 seconds. The
report provides the process names, their process ID (pid), status, CPU
usage, and memory usage.
The report continues to refresh and display in the CLI until you press q (quit).
Once you locate an offending PID, you can terminate it:
diagnose system kill 9 <pid_int>
If
the issue recurs, you can use log messages and/or packet capture to
determine the source of the issue. However, remember that packet capture
itself increases CPU usage.