Technical Report CS-2005-16

Title: Inthreads -- a new computational model to enhance ILP of sequential programs
Authors: Alex Gontmakher, Avi Mendelson, Assaf Schuster and Gregory Shklover
Abstract: This paper presents Inthreads, a new computational model based on sharing the register file that enjoys the benefits of multithreading within the context of a single SMT thread. The model incurs overhead that is orders of magnitude lower than that of conventional threads and therefore supports fine grain parallelization. We present the basic concepts of the Inthreads model, the compilation process, and describe the mechanisms that provide an efficient implementation of thread management and synchronization operations. We take special care of instruction dependenc ies that cross thread boundaries due to the register sharing. Our simulation results indicate that fine granularity threads can be used for different single threaded kernels and applica tions. We reach speedup of up to 2.5x on benchmarks from SPEC and up to 4x on individual code sections. In cases where the memory is the performance bottleneck, we have been able to hide an increase of memory latency from 100 to 400 cycles.
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