Compiler and runtime support for efficient software transactional memory

Abstract

Programmers have traditionally used locks to synchronize concurrent access to shared data. Lock-based synchronization, however, has well-known pitfalls: using locks for fine-grain synchronization and composing code that already uses locks are both difficult and prone to deadlock. Transactional memory provides an alternate concurrency control mechanism that avoids these pitfalls and significantly eases concurrent programming. Transactional memory language constructs have recently been proposed as extensions to existing languages or included in new concurrent language specifications, opening the door for new compiler optimizations that target the overheads of transactional memory. This paper presents compiler and runtime optimizations for transactional memory language constructs. We present a highperformance software transactional memory system (STM) integrated into a managed runtime environment. Our system efficiently implements nested transactions that support both composition of transactions and partial roll back. Our JIT compiler is the first to optimize the overheads of STM, and we show novel techniques for enabling JIT optimizations on STM operations. We measure the performance of our optimizations on a 16-way SMP running multi-threaded transactional workloads. Our results show that these techniques enable transactional memory's performance to compete with that of well-tuned synchronization.

Speculative Program Parallelization with Scalable and Decentralized Runtime Verification

“…Software transactional memory (STM) [17][18][19] was proposed to ensure the correctness of speculative code. STM enables a group of read and write operations to execute atomically, embedded in transactions.…”

“…Despite increasing parallelism (speculatively), STM systems are notorious for the high overhead they introduce. The work of Adl-Tabatabai et al [17] develops compiler and runtime optimizations for transactional memory constructs, using JIT. Static optimizations are employed to expose safe operations, such that redundant STM operations can be removed, while the STM library interface is tailored to handle JIT-compiled and optimized code.…”

Transactional memory

“…McRT-STM [86] is a software transactional memory system for C++ and Java implemented on top of the McRT [3] run-time system. It employs a direct update strategy in combination with early conflict detection for writes and late conflict detection for reads, and supports conflict detection at both cache line and object level.…”

Transactions with isolation and cooperation

“…Our propositional type system easily translates to existing constructs in the Java type system (e.g., require an expose ... establish clause through Java's static check for exception catching). The recent literature is rich with mechanisms applicable in our context for translating transactional extensions down to regular Java [1,30,31,34,40,46]. Therefore, this aspect of the implementation is well-understood, and we concentrate next on elements unique to TIC that are currently captured by our back-end library.…”