Thread-Specific Storage for C/C++ an Object Behavioral Pattern for Accessing Per-Thread State Efficiently

In theory, multi-threading an application can improve performance (by executing multiple instruction streams simultaneously) and simplify program structure (by allowing each thread to execute synchronously rather than reactively or asynchronously). In practice, multi-threaded applications often perform no better, or even worse, than single-threaded applications due to the overhead of acquiring and releasing locks. In addition, multi-threaded applications are hard to program due to the complex concurrency control protocols required to avoid race conditions and deadlocks. This paper describes the Thread-Specific Storage pattern, which alleviates several problems with multi-threading performance and programming complexity. The Thread-Specific Storage pattern improves performance and simplifies multithreaded applications by allowing multiple threads to use one logically global access point to retrieve thread-specific data without incurring locking overhead for each access.