Performance Study of Hyper-Threading Technology on the LUSITANIA Supercomputer

In this paper Hyper-Threading technology is evaluated on the LUSITANIA supercomputer. LUSITANIA is a SMP-ccNUMA system composed of two HP Integrity Super Domes SX2000. The effects of Intel's Hyper-Threading Technology on Intel Itanium processors are not very clear, in order to understand how this technology affects the performance of LUSITANIA, several benchmarks have been studied. Those bechmarks have been carefully chosen to try to demonstrate the performance gain or degradation when running different kind of applications. The results demonstrate that Hyper-Threading achieve better performance when the application needs to communicate data among processes or threads, but, whenever the application is embarrassingly parallel, cache-friendly or all the floating point units are optimized it is not advisable to enable Hyper-Threading. We have also empirically study that the sense of the application will determine whether Hyper-Threading will accelerate or diminish performance. Enabling Hyper-Threading or disabling it is not an exact science, it depends on so many factors that a bechmark study of the problem that is going to be addressed is highly recommended.