Microsoft Technology Licensing, LLC

Avraham E Shinnar

David Read Tarditi, Jr

Timothy Lawrence Harris

Mark Ronald Plesko

Bjarne Steensgaard

A software transactional memory system is described which utilizes decomposed software transactional memory instructions as well as runtime optimizations to achieve efficient performance. The decomposed instructions allow a compiler with knowledge of the instruction semantics to perform optimizations which would be unavailable on traditional software transactional memory systems. Additionally, high-level software transactional memory optimizations are performed such as code movement around procedure calls, addition of operations to provide strong atomicity, removal of unnecessary read-to-update upgrades, and removal of operations for newly-allocated objects. During execution, multi-use header words for objects are extended to provide for per-object housekeeping, as well as fast snapshots which illustrate changes to objects. Additionally, entries to software transactional memory logs are filtered using an associative table during execution, preventing needless writes to the logs. Finally a garbage collector with knowledge of the software transactional memory system compacts software transactional memory logs during garbage collection.

Compiler support for optimizing decomposed software transactional memory operations

Removal of unnecessary read-to-update upgrades in software transactional memory

Existing methods for returning program state to a previous state are often too heavy weight. Often these methods attempt to guarantee a series of properties to a programmer across a distributed environment or multiple threads. Instead, a program state reversion mechanism provides a light weight and efficient runtime solution for general purpose programming languages. For example, a series of program statements (e.g., methods, instructions, etc.) are indicated by a programmer in a state reversion language construct, such as a TryAll block. If an exception is thrown anywhere from within the TryAll block, the program is reverted to the pre-TryAll block state.

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Avraham E Shinnar