Do you know of some performances test of the different ways to get thread local storage in C++?

I'm doing a library that makes extensive use of a thread local variable. Can you point to some benchmarks that test the performances of the different ways to get thread local variables in C++:

• C++0x thre开发者_运维技巧ad_local variables
• compiler extension (Gcc __thread, ...)
• boost::threads_specific_ptr
• pthread
• Windows
• ...

Does C++0x thread_local performs much better on the compilers providing it?

You can always use time.h. Its your friend when testing performance stuff and nothing else is available.

These are typically implemented as a simple offset in an array in the thread's private memory space. So, accessing the thread specific variable X, of type T,

T y = X;

roughly translates to,

T y = *(T*)(cur_thread.local_tbl[key_X]);

which is too simple to expect a wide variation in performance between implementations. That said, if you find any such benchmarks, please follow up here.