Utilization and Saturation
We use terms like utilization and saturation to help quantify resource consump- tion. Utilization measures how busy a resource is and is usually represented as a percentage average over a time interval. Saturation is often a measure of work that has queued waiting for the resource and can be measured as both an average over time and at a particular point in time. For some resources that do not queue, saturation may be synthesized by error counts. Other terms that we use include throughput and hit ratio, depending on the resource type.
Identifying which terms are appropriate for a resource type helps illustrate their characteristics. For example, we can measure CPU utilization and CPU cache hit ratio. Appropriate terms for each resource discussed are defined.