An Evaluation of Thread Migration for Exploiting Distributed Array Locality

Thread migration is one approach to remote memory accesses on distributed memory parallel computers. In thread migration, threads of control migrate between processors to access data local to those processors, while conventional approaches tend to move data to the threads that need them. Migration approaches enhance spatial locality by making large address spaces local, but are less adept at exploiting temporal locality. Data-moving approaches, such as cached remote memory fetches or distributed shared memory, can use both types of locality. We present experimental evaluation of thread migration’s ability to reduce the impact of remote array accesses across distributed-memory computers. Nomadic Threads uses compiler-generated fine-grain threads which either migrate to make data local or fetch cache lines, tolerating latency with multithreading. We compare these alternatives using various array access patterns.