Making the best of temporal locality: Just-in-time renaming and lazy write-back on the cell/b.e

Cell Superscalar (CellSs) provides a simple, flexible and easy programming approach for the Cell Broadband Engine (Cell/B.E.) that automatically exploits the inherent concurrency of applications at a function or task level. The CellSs environment is based on a source-to-source compiler that translates annotated C or Fortran code and a runtime library tailored for the Cell/B.E. that orchestrates the concurrent execution of the application. We introduce a technique called bypassing that allows CellSs to perform core-to-core Direct Memory Access (DMA) transfers for generic applications. In this review we concisely summarize the bypassing practice and introduce two improvements: just-in-time renaming and lazy write-back. These extensions come at no additional cost and potentially increase performance by improving the per-ceived bandwidth of the Element Interconnect Bus (EIB). Experiments on five fundamental linear algebra kernels demon-strate the applicability of these techniques and quantify the benefit that can be reaped. We also present performance results for a first prototype of CellSs with bypassing