metric
also: cost, weight, measurement, KPI (Key Performance Indicator)
A quantifiable measurement or value used to evaluate system performance, network quality, or routing decisions. In Linux, metrics track various aspects like CPU usage, memory consumption, or network path costs.
A metric is a numerical value assigned to measure system characteristics or performance attributes. In networking contexts, metrics determine the cost or priority of routes—lower metrics indicate preferred paths. In system monitoring, metrics represent measurable data like CPU utilization, disk I/O, or network latency.
For example, the ip route command uses metrics to rank multiple routes to the same destination. A route with metric 100 is preferred over one with metric 200. Similarly, monitoring tools collect metrics such as process memory usage or network bandwidth to assess system health.
The term applies broadly: kernel metrics track internal system state, application metrics measure performance, and business metrics evaluate user experience. Linux provides tools like prometheus, telegraf, and /proc filesystem to gather and export metrics for analysis.