Tradeoffs in Buffering Memory State for Thread-Level Speculation in Multiprocessors

Thread-level speculation provides architectural support to aggressively run hard-to-analyze code in parallel. As speculative tasks run concurrently, they generate unsafe or speculative memory state that needs to be separately buffered and managed in the presence of distributed caches and buffers. Such state may contain multiple versions of the same variable. In this paper, we introduce a novel taxonomy of approaches to buffer and manage multi-version speculative memory state in multiprocessors. We also present a detailed complexity-benefit tradeoff analysis of the different approaches. Finally, we use numerical applications to evaluate the performance of the approaches under a single architectural framework. Our key insights are that support for buffering the state of multiple speculative tasks and versions per processor is more complexity-effective than support for merging the state of tasks with main memory lazily. Moreover, both supports can be gainfully combined and, in large mach...

• Type: Conference
• Year: 2003
• Where: HPCA
• Authors: María Jesús Garzarán, Milos Prvulovic, José María Llabería, Víctor Viñals, Lawrence Rauchwerger, Josep Torrellas
• Keywords: Computer Architecture, HPCA 2003, Multi-version Speculative Memory, Multiple Speculative Tasks, Speculative Memory State