How does the Sun JVM map Java threads to Windows threads?

Question

My application uses loads of Java threads. I am looking for a reliable understanding how the JVM (version 5 and 6) maps the Java threads to underlying Windows threads. I know there is a document for mapping to Solaris threads, but not Windows.

Why doesn't Sun publish this information?

I want to know if there's a 1:1 mapping, or if it varies by JVM, by -server option, by workload, etc, etc.

I know I am not "supposed" to care, I should write properly synchronisd code, but I am inheriting a large body of code...

Also, does anyone know how to give names to Windows threads?

Answer 1

Don't have a document for you, but from the Threads column in the task-manager you can pretty reliably guess that it maps 1:1 to native threads (you need to enable the Threads column in the task manger first).

Oh, almost forgot, you can download the jdk src here and look yourself.

Answer 2

The mapping is platform-dependent, however I found an interesting comparison between platform threads for the vm (although probably a bit old). The bottom line is: you don't need to know. What you probably are more interested is to know about green threads (if you don't know already).

As for the naming question: Doesn't the constructor allow you to name a thread? Or do you mean name them and view their name on some windows thread browser?

Answer 3

How to name a Win32 thread

Unfortunately, this seems like it's impossible or at least very hard to do inside the Windows JVM.