Supporting I/O and IPC via fine-grained OS isolation for mixed-criticality real-time tasks

Abstract

Efforts towards hosting safety-critical, real-time applications on multicore platforms have been stymied by a problem dubbed the “one-out-of-m” problem: due to excessive analysis pessimism, the overall capacity of an m-core platform can easily be reduced to roughly just one core. The predominant approach for addressing this problem introduces hardware-isolation techniques that ameliorate contention experienced by tasks when accessing shared hardware components, such as DRAM memory or caches. Unfortunately, in work on such techniques, the operating system (OS), which is a key source of potential interference, has been largely ignored. Most real-time OSs do facilitate the use of a coarse-grained partitioning strategy to separate the OS from user-level tasks. However, such a strategy by itself fails to address any data sharing between the OS and tasks, such as when OS services are required for interprocess communication (IPC) or I/O.This paper presents techniques for lessening the impacts of such sharing, specifically in the context of MC2, a hardware-isolation framework designed for mixed-criticality systems. Additionally, it presents the results from micro-benchmark experiments and a large-scale schedulability study conducted to evaluate the eficacy of the proposed techniques and to elucidate sharing vs. isolation tradeos involving the OS.This is the first paper to systematically consider such tradeos and consequent impacts of OS-induced sharing on the one-out-of-m problem.