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pfSense® software has many built-in graphs that monitor different aspects of the system, and they work out-of-the-box with no intervention.
These are located under Status > Monitoring. Several graphs are presented for each monitored item, with varying time intervals and averages.
These graphs measure things such as CPU usage, memory usage, state table usage, throughput (in bytes as well as packets), link quality, traffic shaping queue usage, and so on.