Logstash Logback Encoder - 为什么 caller info is costly to calculate 呢？

[JasonLaw]

最近使用了logstash/logstash-logback-encoder: Logback JSON encoder and appenders，在Caller Info Fields中，有下面这么一段话。

The encoder/layout/appender do not contain caller info by default. This can be costly to calculate and should be switched off for busy production environments.

为什么说“caller info is costly to calculate”呢？

• [#LOGBACK-809] Logback performance reduced when the log pattern has [%file:%line] - QOS.ch JIRA
• java - Performance Impact of logging class name , method name and line number - Stack Overflow