CSR: Small: Quest: A Real-Time Operating System for Multicore Processors

多核处理器在高端服务器、个人电脑、手机和嵌入式设备中变得无处不在。虽然这些处理器可以提供比单核架构更高的性能和更低的功耗，但它们给系统设计人员带来了巨大的挑战。在实时嵌入式系统中尤其如此，例如在航空电子和汽车控制、制造和医疗保健中。在这些系统中，任务通常有关键的时间要求，必须在最后期限前完成，以避免潜在的灾难性结果。在多核处理器上提供时序保证是困难的，因为共享的片上高速缓存和内存总线带宽的竞争，以及其他影响可预测性的因素，例如硬件中断、指令流水线和同步多线程。这个系统叫？Quest？以时间为中心，作为第一类资源，保证计算资源在所有任务之间的实时共享，包括中断和应用程序线程。该项目使用现代处理器上可用的硬件性能计数器，实现了一个影响资源管理的实时性能监控子系统。该工作的另一个方面是使用硬件沙箱技术来确保系统不会受到编写不当的软件的危害，例如第三方开发人员实现的驱动程序或服务。考虑到现代软件系统的复杂性，仅使用静态方法不能轻松地验证其行为是否正确，这一点尤其相关。作为Quest开发的一部分，将调查硬件虚拟化能力，以增强软件可靠性，特别是隔离系统软件组件的技术，同时确保可预测性，这项工作的结果将影响多核处理器上的系统软件设计。对硬件功能有了更好的了解，以改进或简化软件系统的构建，特别是具有安全关键要求的软件系统。对系统可预测性和安全性的调查将有助于防止关键任务的潜在灾难性后果。这项工作可能导致更强大的系统，以避免因故障而造成的生命、设备或金钱损失。Quest软件将在研究社区之间共享，并在涉及操作系统的课程中使用。

Multicore processors are becoming ubiquitous among high-end servers, personal computers, mobile phones and embedded devices. While these processors can provide higher performance at lower power than single-core architectures, they pose significant challenges for system designers. This is particularly true in real-time embedded systems, such as in avionic and automotive control, manufacturing, and healthcare. In these systems, tasks often have critical timing requirements, with deadlines that must be met to avoid potentially catastrophic outcomes. Providing timing guarantees on multicore processors is made difficult by contention for shared on-chip caches and memory bus bandwidth, and other factors such as hardware interrupts, instruction pipelines and simultaneous multithreading that affect predictability.This project focuses on the design of a real-time operating system that addresses micro-architectural resource contention and enforces predictable behavior on multicore processors. This system called ?Quest? is centered around time as a first class resource, guaranteeing real-time shares of computational resources among all tasks, including interrupts and application threads. Using hardware performance counters available on modern processors, this project implements a real-time performance monitoring subsystem to influence resource management.An additional aspect of this work focuses on the use of hardware sandboxing techniques to guarantee the system is not compromised by ill-written software, such as drivers or services implemented by third party developers. This is especially relevant given the complexity of modern software systems that cannot easily be verified to behave correctly using only static methods. As part of the development of Quest, hardware virtualization capabilities are investigated to enforce heightened software reliability, in particular, techniques for isolating software components of a system, while ensuring predictability, The outcomes of this work will impact the design of systems software on multicore processors. A greater understanding of hardware features to improve or ease the construction of software systems is gained, especially those with safety-critical requirements. Investigations into system predictability and safety will help prevent potentially disastrous outcomes for mission-critical tasks. This work could lead to more robust systems that avoid costs of failure in terms of loss of lives, equipment, or money. The Quest software will be shared among the research community and used in courses involving operating systems.