Putting Hard Real-time Applications together with Dark Silicon
Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
As the number of transistors per unit square on silicon chips continues to in- crease, the heat production of these chips also increases, making thermal problems more common. As the heat production is dependent on the clock frequency, chips today have a defined thermal safe speed at which the cooling system is sufficient to compensate for the produced heat. A DVFS enabled processor executing at speeds over the thermal safe speed for prolonged periods of time may be forced to power down a set of cores to prevent damage due to overheating. As any deadline violations are considered as a system failure, executing hard real-time workloads on such a platform is not trivial. This thesis presents an online scheme which enables the execution of workloads on such a system. The scheme uses a history aware bounding function for determining when the processor speed must be increased above the thermal safe speed, and as such has a constant and small memory and computation footprint. The scheme is analysed using predefined traces within the gem5 simulator. For this purpose a new simulated hardware device is implemented which allows the scheduler to read predefined trace files. With workloads that follow the model closely the online scheme performs on-par with the optimal offline implementation. For workloads whose arrival curve follow the model less closely, the presented scheme is still able to assign timing correct processor speeds.
Place, publisher, year, edition, pages
2015. , 48 p.
UPTEC IT, ISSN 1401-5749 ; 15016
Engineering and Technology
IdentifiersURN: urn:nbn:se:uu:diva-268030OAI: oai:DiVA.org:uu-268030DiVA: diva2:875516
Kaxiras, StefanosNordén, Lars-Åke