Software behavior oriented parallelization

Many sequential applications are difficult to parallelize because of unpredictable control flow, indirect data access, and input-dependent parallelism. These difficulties led us to build a software system for behavior oriented parallelization (BOP), which allows a program to be parallelized based on partial information about program behavior, for example, a user reading just part of the source code, or a profiling tool examining merely one or few executions. The basis of BOP is programmable software speculation, where a user or an analysis tool marks possibly parallel regions in the code, and the run-time system executes these regions speculatively. It is imperative to protect the entire address space during speculation. The main goal of the paper is to demonstrate that the general protection can be made cost effective by three novel techniques: programmable speculation, critical-path minimization, and value-based correctness checking. On a recently acquired multicore, multi-processor PC, the BOP system reduced the end-to-end execution time by integer factors for a Lisp interpreter, a data compressor, a language parser, and a scientific library, with no change to the underlying hardware or operating system.