Troubleshooting High CPU Load

First, open a shell from ssh or the serial/VGA console (option 8).

Run the following commands:

To view the top processes, including interrupt processing CPU usage and system CPU:

# top -aSH

To view the interrupt counters and other system usage:

# systat -vmstat 1

To view the mbuf usage:

# netstat -m

(Alternately, check the dashboard mbuf counter, and the graph under Status > RRD Graphs on the System tab)

To view I/O operations:

# systat -iostat 1


# top -aSH
  • Then press m to switch to I/O mode to view disk activity

Typically one of these commands will include some obvious consumer of large amounts of system resources. For example, if the system CPU usage is high, it may be pf. If a VPN process is using lots of CPU, the hardware may not be able to process more VPN traffic. If it is a NIC, see Tuning and Troubleshooting Network Cards, etc.

If the solution is not obvious based on the output, post the collected information on the forum or mailing list or contact support for further assistance.