Where is time spent in message-passing and shared-memory programs?
ASPLOS VI Proceedings of the sixth international conference on Architectural support for programming languages and operating systems
The performance advantages of integrating block data transfer in cache-coherent multiprocessors
ASPLOS VI Proceedings of the sixth international conference on Architectural support for programming languages and operating systems
The SPLASH-2 programs: characterization and methodological considerations
ISCA '95 Proceedings of the 22nd annual international symposium on Computer architecture
SoftFLASH: analyzing the performance of clustered distributed virtual shared memory
Proceedings of the seventh international conference on Architectural support for programming languages and operating systems
CAS-DSM: a compiler assisted software distributed shared memory
International Journal of Parallel Programming
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We examine the performance benefits of integrating a mechanism for block data transfer (message passing) in a cache-coherent shared address space multiprocessor. We do this through a detailed study of five important computations that appear to be likely candidates for block transfer. We find that while the benefits on a realistic architecture are significant in some cases, they are not as substantial as one might initially expect. The main reasons for this are (i) the relatively modest fraction of time that applications spend in communication that is amenable to block transfer, (ii) the difficulty of finding enough independent computation to overlap with the communication latency that remains even after block transfer, and (iii) the fact that long cache lines often capture many of the benefits of block transfer. Of the three primary advantages of block transfer, fast pipelined data transfer appears to be the most successful, followed by the ability to overlap computation and communication at a coarse granularity, and finally the benefits of replicating communicated data in main memory. We also examine the impact of varying important network parameters and processor speed on the relative effectiveness of block transfer, and comment on useful features that a block transfer engine should support for real applications.