System Activity (Top)

The Diagnostics > System Activity page displays several aspects of system activity as reported by top which are updated every few seconds. This is equivalent to running the command top -aSH at a shell prompt.

The output contains several key types of information:

  • The system load average.

  • A total count of processes in various states (running, sleeping, waiting, etc.).

  • The current CPU usage.

  • A breakdown of memory usage in various areas.

    See also

    See Memory Management for details on each area.

  • ZFS ARC usage breakdown, if the system contains any active ZFS pools.

    See also

    See ZFS Tuning for information on reducing this if necessary.

  • Swap memory usage.

  • A list of the active processes running on the firewall.

Using this view it is easy to see processes that consume the most CPU power during a time of high load. For example, if the highest entry is an interrupt processing queue for one of the network cards, and the system isn’t passing enough traffic, it could be one sign that the firewall is trying to push more than the hardware can handle in the current configuration. If the top process is a PHP process, it could be that a browser has requested a GUI page that is processing a large amount of data.


Threads that show idle in the COMMAND column indicate CPU time that is not in use (idle). It is normal for these to show 100% if the firewall has little to no load.