<jats:p> Robust and powerful software instrumentation tools are essential for program analysis tasks such as profiling, performance evaluation, and bug detection. To meet this need, we have developed a new instrumentation system called <jats:italic>Pin</jats:italic> . Our goals are to provide <jats:italic>easy-to-use, portable, transparent</jats:italic> , and <jats:italic>efficient</jats:italic> instrumentation. Instrumentation tools (called <jats:italic>Pintools</jats:italic> ) are written in C/C++ using Pin's rich API. Pin follows the model of ATOM, allowing the tool writer to analyze an application at the instruction level without the need for detailed knowledge of the underlying instruction set. The API is designed to be <jats:italic>architecture independent</jats:italic> whenever possible, making Pintools source compatible across different architectures. However, a Pintool can access architecture-specific details when necessary. Instrumentation with Pin is mostly <jats:italic>transparent</jats:italic> as the application and Pintool observe the application's original, uninstrumented behavior. Pin uses <jats:italic>dynamic compilation</jats:italic> to instrument executables while they are running. For efficiency, Pin uses several techniques, including inlining, register re-allocation, liveness analysis, and instruction scheduling to optimize instrumentation. This fully automated approach delivers significantly better instrumentation performance than similar tools. For example, Pin is 3.3x faster than Valgrind and 2x faster than DynamoRIO for basic-block counting. To illustrate Pin's versatility, we describe two Pintools in daily use to analyze production software. Pin is publicly available for Linux platforms on four architectures: IA32 (32-bit x86), EM64T (64-bit x86), Itanium®, and ARM. In the ten months since Pin 2 was released in July 2004, there have been over 3000 downloads from its website. </jats:p>