Quantifying contention and balancing memory load on hardware DSM multiprocessors

This paper makes the following contributions: It proposes a new methodology for quantifying remote memory access contention on hardware DSM multiprocessors. The most valuable aspect of this methodology is that it assesses the overhead of contention on real parallel programs running on real hardware. The methodology uses as input the number of accesses from each node of the DSM to each page in memory. A trace of the memory accesses of the program obtained at runtime is used to compute a fairly accurate estimate of the fraction of execution time wasted due to contention. The paper presents also a new algorithm which detects potential hot spots in pages and balances memory load using dynamic page migration. The algorithm attacks indirectly the problem of contention by balancing the remote memory access latency across the nodes of the system. Experiments with five irregular parallel codes on a 128-processor Origin2000 show that the algorithm yields significant performance improvements. r 2003 Published by Elsevier Inc.