Supporting Differentiated Services in Computers via Programmable Architecture for Resourcing-on-Demand (PARD)

This paper presents PARD, a programmable architecture for resourcing-on-demand that provides a new programming interface to convey an application's high-level information like quality-of-service requirements to the hardware. PARD enables new functionalities like fully hardware-supported virtualization and differentiated services in computers. PARD is inspired by the observation that a computer is inherently a network in which hardware components communicate via packets (e.g., over the NoC or PCIe). We apply principles of software-defined networking to this intra-computer network and address three major challenges. First, to deal with the semantic gap between high-level applications and underlying hardware packets, PARD attaches a high-level semantic tag (e.g., a virtual machine or thread ID) to each memory-access, I/O, or interrupt packet. Second, to make hardware components more manageable, PARD implements programmable control planes that can be integrated into various shared resources (e.g., cache, DRAM, and I/O devices) and can differentially process packets according to tag-based rules. Third, to facilitate programming, PARD abstracts all control planes as a device file tree to provide a uniform programming interface via which users create and apply tag-based rules. Full-system simulation results show that by co-locating latencycritical memcached applications with other workloads PARD can improve a four-core computer's CPU utilization by up to a factor of four without significantly increasing tail latency. FPGA emulation based on a preliminary RTL implementation demonstrates that the cache control plane introduces no extra latency and that the memory control plane can reduce queueing delay for high-priority memory-access requests by up to a factor of 5.6.