Thread-local storage

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In computer programming, thread-local storage (TLS) is a memory management method that uses static or global memory local to a thread. The concept allows storage of data that appears to be global in a system with separate threads.

Many systems impose restrictions on the size of the thread-local memory block, in fact often rather tight limits. On the other hand, if a system can provide at least a memory address (pointer) sized variable thread-local, then this allows the use of arbitrarily sized memory blocks in a thread-local manner, by allocating such a memory block dynamically and storing the memory address of that block in the thread-local variable. On RISC machines, the calling convention often reserves a thread pointer register for this use.