Comparability graph coloring for optimizing utilization of stream register files in stream processors

Abstract

A stream processor executes an application that has been decomposed into a sequence of kernels that operate on streams of data elements. During the execution of a kernel, all streams accessed must be communicated through the SRF (Stream Register File), a non-bypassing software-managed on-chip memory. Therefore, optimizing utilization of the SRF is crucial for good performance. The key insight is that the interference graphs formed by the streams in stream applications tend to be comparability graphs or decomposable into a set of multiple comparability graphs. We present a compiler algorithm that can find optimal or near-optimal colorings in stream IGs, thereby improving SRF utilization than the First-Fit bin-packing algorithm, the best in the literature.