LCM: memory system support for parallel language implementation

  • Authors:

  • James R. Larus;Brad Richards;Guhan Viswanathan

  • Affiliations:

  • Computer Sciences Department, University of Wisconsin-Madison, 1210 West Dayton Street, Madison, WI, USA;Computer Sciences Department, University of Wisconsin-Madison, 1210 West Dayton Street, Madison, WI, USA;Computer Sciences Department, University of Wisconsin-Madison, 1210 West Dayton Street, Madison, WI, USA

  • Venue:
  • ASPLOS VI Proceedings of the sixth international conference on Architectural support for programming languages and operating systems
  • Year:
  • 1994

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Abstract

Higher-level parallel programming languages can be difficult to implement efficiently on parallel machines. This paper shows how a flexible, compiler-controlled memory system can help achieve good performance for language constructs that previously appeared too costly to be practical.Our compiler-controlled memory system is called Loosely Coherent Memory (LCM). It is an example of a larger class of Reconcilable Shared Memory (RSM) systems, which generalize the replication and merge policies of cache-coherent shared-memory. RSM protocols differ in the action taken by a processor in response to a request for a location and the way in which a processor reconciles multiple outstanding copies of a location. LCM memory becomes temporarily inconsistent to implement the semantics of C** parallel functions efficiently. RSM provides a compiler with control over memory-system policies, which it can use to implement a language's semantics, improve performance, or detect errors. We illustrate the first two points with LCM and our compiler for the data-parallel language C**.