We present HyFlow - a distributed software transactional memory (D-STM) framework for distributed concurrency control. Lock-based concurrency control suffers from drawbacks including deadlocks, livelocks, and scalability and composability challenges. These problems are exacerbated in distributed systems due to their distributed versions which are more complex to cope with (e.g., distributed deadlocks). STM and D-STM are promising alternatives to lock-based and distributed lock-based concurrency control for centralized and distributed systems, respectively, that overcome these difficulties. HyFlow is a Java framework for DSTM, with pluggable support for directory lookup protocols, transactional synchronization and recovery mechanisms, contention management policies, cache coherence protocols, and network communication protocols. HyFlow exports a simple distributed programming model that excludes locks: using (Java 5) annotations, atomic sections are defiend as transactions, in which reads and writes to shared, local and remote objects appear to take effect instantaneously. No changes are needed to the underlying virtual machine or compiler. We describe HyFlow's architecture and implementation, and report on experimental studies comparing HyFlow against competing models including Java remote method invocation (RMI) with mutual exclusion and read/write locks, distributed shared memory (DSM), and directory-based D-STM. / Master of Science

La nueva tendencia para aumentar el rendimiento de los futuroscomputadores son los multiprocesadores en un solo chip (CMPs). Seespera que en un futuro cercano salgan al mercado CMPs con decenas deprocesadores. Hoy en d�a, la mejor manera de mantener la coherencia decache en estos sistemas es mediante los protocolos basados endirectorio. Sin embargo, estos protocolos tienen dos grandesproblemas: una gran sobrecarga de memoria y una alta latencia de losfallos de cache.Esta tesis se ha centrado en estos problemas claves para la eficienciay escalabilidad del CMP. En primer lugar, se ha presentado unaorganizaci�n de directorios escalable. En segundo lugar, se hanpropuesto los protocolos de coherencia directa, que evitan laindirecci�n al nodo home y, por tanto, reducen el tiempo de ejecuci�nde las aplicaciones. Por �ltimo, se ha desarrollado una pol�tica demapeo para caches compartidas pero f�sicamente distribuidas, quereduce la latencia de acceso y garantiza una distribuci�n uniforme delos datos con el fin de reducir su tasa de fallos. Esto se traducefinalmente en un menor tiempo de ejecuci�n para las aplicaciones. / Chip multiprocessors (CMPs) constitute the new trend for increasingthe performance of future computers. In the near future, chips withtens of cores will become more popular. Nowadays, directory-basedprotocols constitute the best alternative to keep cache coherence inlarge-scale systems. Nevertheless, directory-based protocols have twoimportant issues that prevent them from achieving better scalability:the directory memory overhead and the long cache miss latencies.This thesis focuses on these key issues. The first proposal is ascalable distributed directory organization that copes with the memoryoverhead of directory-based protocols. The second proposal presentsthe direct coherence protocols, which are aimed at avoiding theindirection problem of traditional directory-based protocols and,therefore, they improve applications' performance. Finally, a novelmapping policy for distributed caches is presented. This policyreduces the long access latency while lessening the number of off-chipaccesses, leading to improvements in applications' execution time.