Performance Tuning of Small Scale Shared Memory Multiprocessor Applications using Visualisation

Even though shared memory multiprocessors are becoming more and more common, it is still a formidable task to achieve high performance on parallel applications. One of the main reasons for this is a high amount of implicit communication generated by the program due to poor structuring of the program. This article shows the importance of performance visualisation in order to spot and find the source of cache coherence bottlenecks. This is exemplified by a performance analysis tool, SMprof, that visualises accesses to shared data structures so that problematic access patterns are highlighted. SM-prof maintains links from the visualisation to the actual source code lines responsible for the accesses. In contrast to earlier approaches, SM-prof shows the inherent data sharing of the application that would occur in any shared memory architecture. We demonstrate the merits of SM-prof by means of two detailed case studies.