Publication

Current mainstream processors provide multiple SMT (i.e., simultaneous multithreading) lanes on top of each physical core. These hardware threads share more resources (e.g., execution units and caches) when compared to CPU cores, but are managed by operating systems in the same way as if they were separate physical cores. This Thesis explores the interaction between hardware threads and proposes an extension to the Barrelsh OS, meant to improve the performance of a system by adequately handling SMT lanes. On an Intel Haswell CPU, with 2-way SMT via Hyper-Threading Technology, each SMT lane had 2=3 of the processing power that was yielded by the physical core with a single active hardware thread. The multi-HT CPU Driver (i.e., Barrelsh's microker-nel) is able to modify the set of active hardware threads with an overhead in the order of thousands of processor cycles, which means that it can quickly adapt to the parallelism exhibited by the workload.

@mastersthesis{abc,
	abstract = {Current mainstream processors provide multiple SMT (i.e., simultaneous multithreading) lanes on top of each physical core. These hardware threads share more resources (e.g., execution units and caches) when compared to CPU cores, but are managed by operating systems in the same way as if they were separate physical cores. This Thesis explores the interaction between hardware threads and proposes an extension to the Barrelsh OS, meant to improve the performance of a system by adequately handling SMT lanes. On an Intel Haswell CPU, with 2-way SMT via Hyper-Threading Technology, each SMT lane had 2=3 of the processing power that was yielded by the physical core with a single active hardware thread. The multi-HT CPU Driver (i.e., Barrelsh{\textquoteright}s microker-nel) is able to modify the set of active hardware threads with an overhead in the order of thousands of processor cycles, which means that it can quickly adapt to the parallelism exhibited by the workload.},
	author = {Andrei Poenaru},
	school = {161},
	title = {Explicit OS support for hardware threads},
	year = {2017}
}