The theme of the workshop was “efficient modelling of parallel computer systems”, with special attention being given to the modelling of performance and power usage of parallel technologies. The first talk of the workshop, presented by Thomas Ilsche from the Technical University of Dresden, addressed the issue of energy monitoring on large-scale HPC system. The talk discussed methods for measuring energy usage through the integration of vendor specific energy counters with the Score-P measurement infrastructure, and contrasted real-life measurements with predictions from models such as RAPL. Lieven Eeckhout from Ghent University then followed with a presentation on the advantages of interval performance models for modern processors. The models are crucial when attempting to either design more efficient or powerful processors, or to develop runtime systems that can optimise for performance and power efficiency. Both talks were extremely well received and both speakers were met with numerous questions about their work.
After the coffee break, Stefanos Kaxiras from the University of Uppsala presented techniques for saving power by exploiting dynamic frequency voltage scaling (DVFS) through decoupling of L1 cache data prefetches from L1 cache data use. He also described the limitations imposed by current hardware, which for instance only supports DVFS on a per-CPU and not a per-core basis. The next speaker, Nick Johnson from EPCC at the University of Edinburgh, took a step back and discussed the wider motivations for performance and power modelling. He gave an overview of the state-of-the-art and introduced the Adept project and its key objectives within this context. The final talk of the workshop was presented by David Black-Schaeffer from Uppsala University, who introduced recent advances in the performance of full system simulation, a process that is extremely resource intensive, using the Gem5 microarchitecture simulator.
As Adept is a fairly new project and this was the first time we organised this workshop, the HiPEAC conference allocated us to a small room with a maximum capacity of 20. However for large stretches of the workshop there were twice as many people attending – despite filling the room with more chairs during the coffee break, people still had to stand at the side or in the doorway. This demonstrated to us that the workshop topic and the presentations clearly hit a chord with the conference attendees. The questions that were asked and the feedback that was given after the talks were very useful to the project, and it was encouraging to see the great amount of interest the workshop generated. Adept will continue its research into power and performance modelling, and hopefully we will be back at HiPEAC 2015 to present our progress.