An analysis of dynamic page placement on a NUMA multiprocessor

Abstract

The class of NUMA (nonuniform memory access time) shared memory architectures is becoming increasingly important with the desire for larger scale multiprocessors. In such machines, the placement and movement of code and data are crucial to performance. The operating system can play a role in managing placement through the policies and mechanisms of the virtual memory subsystem. In this paper, we develop an analytic model of memory system performance of a Local/Remote NUMA architecture based on approximate mean-value analysis techniques. The model assumes that a simple workload model based on a few parameters can often provide insight into the general behavior of real applications. The model is validated against experimental data obtained with the DUnX operating system kernel for the BBN GP1000 while running a synthetic workload. The results of this validation show that in general, model predictions are quite good, though in some cases the model fails to include the effect of unexpected behaviors in the implementation. Experiments investigate the effectiveness of dynamic multiple-copy page placement. We investigate the cost of incorrect policy decisions by introducing different percentages of policy error and measuring their effect on performance.