概念概述
USE 方法分析资源（The USE Method for Resource Analysis）指的是：USE 方法逐一检查每个资源的使用率、饱和度与错误，把模糊的性能抱怨转化为系统化的排查清单。
从更严格的定义看，The USE method is a checklist that, for each resource, asks about utilisation, saturation, and errors, providing a structured way to find bottlenecks rather than guessing. 该概念在工程实践中的价值，在于它能帮助团队用统一的语言描述一个具体的质量属性或设计约束，从而在评审与协作中减少歧义。
为什么需要它
It is used during performance investigations on hosts, databases, and network interfaces where the culprit is unknown. 它与 Symptom-Based Alerting、Trace Context Propagation、Exemplars Linking Metrics to Traces 等概念经常一起出现，用于解决相近的工程问题。理解它的适用场景，有助于在多种备选方案之间做出有依据的取舍，而不是凭直觉选择技术方案。
常见误解
- USE is a tool rather than a reasoning checklist
- saturation is only visible when utilisation reaches one hundred percent
需要避免的反模式
- looking only at CPU and ignoring I/O, memory, and connections
- declaring a resource healthy because errors are zero
实践要点
- Utilisation is the average busy time of a resource, saturation is the degree to which it has work queued it cannot service, and errors are failed operations.
- A resource can be saturated before it is fully utilised because of bursty demand or queueing, so measuring only utilisation misses the bottleneck.
- Walking every resource in turn prevents the tunnel vision that leads teams to optimise a component that was never the constraint.