java - @sun.misc.Contended 注释的值是多少？

Question

在 java-8 中出现了新的注解 @sun.misc.Contended。

有几篇写得很好的文章，解释了它的作用和使用方法:

• What is @Contended and False Sharing ?
• @Contended (a.k.a. JEP 142)
• Java @Contended annotation to help reduce false sharing

但是哪里都没有说明，这个注解的value是什么？我的意思是，例如在 java.lang.Thread 中，它的用法如下:

@sun.misc.Contended("tlr")
int threadLocalRandomProbe;

这个 "tlr" 值是多少？它有什么影响？如果此 value 为默认值(空)，会发生什么情况？

Answer 1

取自grepcode.com -> Contended :

A @Contended field annotation may optionally include a contention group tag. A contention group defines a set of one or more fields that collectively must be isolated from all other contention groups. The fields in the same contention group may not be pairwise isolated. With no contention group tag (or with the default empty tag: "") each @Contended field resides in its own distinct and anonymous contention group.

值记录在

The (optional) contention group tag. This tag is only meaningful for field level annotations.

因此 "tlr" 只是为此 int threadLocalRandomProbe 选择的组名称 - 如果您使用相同的组标签注释第二个变量，它们将被组合在一起并且一起隔离。