PatternLayout（log4j）的C，F，L，l和M有多慢？ [英] Exactly how slow are C, F, L, l and M of PatternLayout (log4j)?

问题描述

常见的知识是 C ， F ， L ， l 和 M PatternLayout 很慢：

It's common knowledge that C, F, L, l and M of PatternLayout are slow:

警告生成来电者位置信息是非常缓慢，应该避免，除非执行速度不是问题。

WARNING Generating caller location information is extremely slow and should be avoided unless execution speed is not an issue.

另外，这本书提到一些应用程序只能从更改日志记录格式获得10％的速度。

Also, this book mentions that some applications can gain 10% speed only from changing the logging format.

但问题是，这些转换字符？

But the question is, exactly how slow are these conversion characters?

推荐答案

我使用FileAppender在本地计算机上测量。我很好地预热了测试，测量了许多执行和平均（相对一致的）结果。循环包含 execs ++; log.info（t）; 确切的数字并不重要（因为它依赖于我的电脑），而是比例。我在Java 1.6.0_10（Client VM）上使用了log4j-1.2.16.jar。

I measured locally on my computer using a FileAppender. I warmed up the test nicely, measured many executions and averaged the (relatively consistent) results. The loop contained execs++;log.info("t");The exact numbers do not matter (because they depend on my computer) but proportions do. I used log4j-1.2.16.jar on Java 1.6.0_10 (Client VM).

事实证明，每当 C， F，L，l或M 出现在模式中，日志记录速度至少要慢5倍。

It turns out that whenever any of the C, F, L, l or M appeared in the pattern, logging was at least 5 times slower.

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