Assessing Memory Access Performance of Chapel through Synthetic Benchmarks

Abstract

The Partitioned Global Address Space(PGAS) programming model strikes a balance between high performance and locality awareness. As a PGAS language, Chapel relieves programmers from handling details of data movement in a distributed memory environment, by presenting a flat memory space that is logically partitioned among executing entities. Traversing such a space requires address mapping to the system virtual address space, and as such, this abstraction inevitably causes major overheads during memory accesses. In this paper, we analyzed the extent of this overhead by implementing a micro benchmark to test different types of memory accesses that can be observed in Chapel. We showed that, as the locality gets exploited speedup gains up to 35x can be achieved. This was demonstrated through hand tuning, however. More productive means should be provided to deliver such performance improvement without excessively burdening programmers. Therefore, we also discuss possibilities to increase Chapel's performance through standard libraries, compiler, runtime and/or hardware support to handle different types of memory accesses more efficiently.