Parabilis: Speeding up Single-Threaded Applications by Extracting Fine-Grained Threads for Multi-core Execution

The trend in architectural designs has been towards using simple cores for building multicore chips, instead of a single complex out-of-order (OOO) core, due to the increased complexity and energy requirements of out of order processors. Multicore chips provide better performance when compared with OOO cores while executing parallel applications. However, they are not able to exploit the parallelism inherent in single threaded applications. To this end, this paper presents a compiler optimization methodology coupled with minimal hardware extensions to extract simple fine-grained threads from a single-threaded application, for execution on multiple cores of a chip multiprocessor (CMP). These fine-grained threads are independent and eliminate the need for communication between cores, reducing costly communication latencies. This approach, which we call Parabilis is scalable for up to eight cores, and does not require complex hardware additions to simple multicore systems. Our evaluation shows that Parabilis yields an average speedup of 1.51 on an 8-core CMP architecture.