USE method
also: Utilization Saturation Errors
A systematic performance troubleshooting methodology that prioritizes investigating resource utilization (CPU, memory, disk I/O, network) and saturation before diving into deeper analysis, developed by Brendan Gregg.
The USE method stands for Utilization, Saturation, Errors. It's a practical framework for identifying performance bottlenecks by checking three metrics for each system resource: how much is being used, whether the resource is over-capacity (saturated), and whether errors are occurring.
For example, to troubleshoot a slow system, you'd check CPU utilization (e.g., with top), CPU saturation (run queue length via uptime), and CPU errors (context switches in /proc/stat). This prioritized approach avoids wasting time on irrelevant metrics and quickly reveals where the actual constraint lies.
The USE method is especially valuable because it encourages systematic thinking rather than random tool usage, making it effective for both quick diagnostics and deep performance investigations.