The CPU usage metric shows the percentage of CPU utilised on your node. The percentage shown is the percentage of total CPU available (ie the maximum possible is 100% no matter how many CPU cores in the node).
High CPU usage is one indicator of a node reaching the limits of its processing capacity.
If you are experiencing consistently high CPU usage and not reaching the desired throughput on your Cassandra cluster you may need to tune your data model or add nodes to your cluster to increase processing capacity.
Please contact Instaclustr Support should you have any questions regarding this metric or the processing capacity of your cluster.