Limits of region-based dynamic binary parallelization

Abstract

Efficiently executing sequential legacy binaries on chip multi-processors (CMPs) composed of many, small cores is one of today's most pressing problems. Single-threaded execution is a suboptimal option due to CMPs' lower single-core performance, while multi-threaded execution relies on prior parallelization, which is severely hampered by the low-level binary representation of applications compiled and optimized for a single-core target. A recent technology to address this problem is Dynamic Binary Parallelization (DBP), which creates a Virtual Execution Environment (VEE) taking advantage of the underlying multicore host to transparently parallelize the sequential binary executable. While still in its infancy, DBP has received broad interest within the research community. The combined use of DBP and thread-level speculation (TLS) has been proposed as a technique to accelerate legacy uniprocessor code on modern CMPs. In this paper, we investigate the limits of DBP and seek to gain an understanding of the factors contributing to these limits and the costs and overheads of its implementation. We have performed an extensive evaluation using a parameterizable DBP system targeting a CMP with light-weight architectural TLS support. We demonstrate that there is room for a significant reduction of up to 54% in the number of instructions on the critical paths of legacy SPEC CPU2006 benchmarks. However, we show that it is much harder to translate these savings into actual performance improvements, with a realistic hardware-supported implementation achieving a speedup of 1.09 on average.