Virtual-CPU Scheduling in the Quest Operating System

This paper describes the scheduling framework for a new operating system called “Quest”. The three main goals of Quest are to ensure safety, predictability and efficiency of software execution. For this paper, we focus on one aspect of predictability, involving the integrated management of tasks and I/O events such as interrupts. Quest’s scheduling infrastructure is based around the concept of a virtual CPU (VCPU). Using both Main and I/O VCPUs, we are able to separate the CPU bandwidth consumed by tasks from that used to complete I/O processing. We introduce a priority-inheritance bandwidth-preserving server policy for I/O management, called PIBS. We show how PIBS operates with lower cost and higher throughput than a comparable Sporadic Server for managing I/O transfers that require small bursts of CPU time. Using a hybrid system of Sporadic Servers for Main VCPUs, and PIBS for I/O VCPUs, we show how to maintain temporal isolation between multiple tasks and I/O transfers from ...

• Type: Journal
• Year: 2011
• Where: RTAS
• Authors: Matthew Danish, Ye Li, Richard West
• Keywords: CPU Bandwidth, Embedded Systems, Priority Inheritance, RTAS 2011, Temporal Isolation