Comparative Performance Evaluation of Non-Contiguous Allocation Algorithms in 2D Mesh-Connected Multicomputers

Abstract

Several noncontiguous allocation policies have been proposed for 2D mesh-connected multicomputers. These allocation policies differ in their ability to detect free submeshes and in the degree of contiguity that exists among the submeshes they allocate to the same job. The previous Adaptive Noncontiguous Allocation (ANCA) policy was evaluated based on a proposed formula that estimates the job execution time when the job is allocated noncontiguous submeshes. Using this formula, simulation results had shown that ANCA could outperform the preceding Multiple Buddy Strategy (MBS). However, the execution times of jobs under noncontiguous allocation depend on message sizes, the number of messages sent, message contention and distances messages traverse. In this paper, we evaluate ANCA for different communication patterns using an event-driven simulator operating at the flit level, which allows for a more realistic evaluation that takes into account the shape of allocation and contention among messages. Moreover, we compare the performance of ANCA with that of other noncontiguous allocation strategies (MBS, GABL, and Paging(0)). The results show that ANCA is inferior to the remaining policies, and that GABL has the best performance results, expressed in terms of the average turnaround time and mean system utilization performance parameters.