Unbounded Transactional Memory

Hardware transactional memory should support unbounded transactions: transactions of arbitrary size and duration. We describe a hardware implementation of unbounded transactional memory, called UTM, which exploits the common case for performance without sacrificing correctness on transactions whose footprint can be nearly as large as virtual memory. We performed a cycleaccurate simulation of a simplified architecture, called LTM. LTM is based on UTM but is easier to implement, because it does not change the memory subsystem outside of the processor. LTM allows nearly unbounded transactions, whose footprint is limited only by physical memory size and whose duration by the length of a timeslice. We assess UTM and LTM through microbenchmarking and by automatically converting the SPECjvm98 Java benchmarks and the Linux 2.4.19 kernel to use transactions instead of locks. We use both cycle-accurate simulation and instrumentation to understand benchmark behavior. Our studies show that the co...

• Type: Conference
• Year: 2005
• Where: HPCA
• Authors: C. Scott Ananian, Krste Asanovic, Bradley C. Kuszmaul, Charles E. Leiserson, Sean Lie
• Keywords: Computer Architecture, HPCA 2005, Large Transactions, Unbounded Transactional Memory, Unbounded Transactions