JVM Anatomy Quark #26: Identity Hash Code

• V8

  26 19,491 10.0 C++

  The official mirror of the V8 Git repository

  

  Yeah, I know that trick. I implemented an identity hashmap[1] inside of V8 that uses that, because JS objects don't have an identity hash code[2]. It uses the object address as the basis of the hash code, which means the table needs to be reorganized when the GC moves objects, which is done with a post-GC hook. The identity maps in V8 are generally short-lived.

  I am not aware of production JVMs that use this, because in the worst case they can use a lot more memory if a lot of objects end up needing hashcodes.

  [1] https://github.com/v8/v8/blob/dc712da548c7fb433caed56af9a021...

• JDK

  59 13,022 10.0 Java

  JDK main-line development

  

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