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Real-time operating system services for networked embedded systems.

机译：用于网络嵌入式系统的实时操作系统服务。

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This dissertation examines issues related to the design and implementation of real-time operating system (RTOS) services for consumer item embedded systems such as cars, webTVs, and cellular phones. Since these devices are mass-produced, keeping production costs low is all important, meaning that RTOS services must be highly efficient to enable use of low-cost hardware in these devices. This dissertation explores optimization techniques for basic RTOS services (task scheduling, synchronization, and communication) to meet the requirements of embedded systems.; First, dynamic schedulers like earliest-deadline first (EDF) give high processor utilization but incur high run-time overhead while the opposite is true for static schedulers like rate-monotonic (RM). We design the combined static/dynamic (CSD) scheduler which employs both EDF and RM to deliver run-time overhead comparable to RM and utilization comparable to EDF.; Second, increasing use of OO programming has made efficient synchronization important for embedded systems. In an OO multitasking environment, accesses to objects have to be protected through semaphores to ensure mutual exclusion. We present a new semaphore implementation scheme which saves one context switch per lock operation in most circumstances by rescheduling threads to minimize blocking.; Third, embedded devices with Internet connectivity require efficient processing of network data. We present a protocol architecture for reducing receive overhead for audio and video messages. The architecture reduces I-cache misses by safely bypassing multiple protocol layers (benefiting short audio messages) and real-time message data is copied only once without any hardware support (benefiting long video messages).; Finally, embedded systems incoporating local area networks (LANs) require proper LAN message scheduling. Controller Area Network (CAN) is a popular LAN in automotive applications. Pure EDF scheduling is not feasible for CAN because of unacceptable overhead while deadline-monotonic (DM) scheduling is feasible but yields low network utilization. We present the feasible mixed traffic scheduler (MTS) which combines EDF and DM using quantized deadlines to deliver higher utilization than DM.; Using these optimizations, we built and evaluated an RTOS that provides a rich set of services to programmers and meets the efficiency/cost requirements of embedded systems.
机译：本文研究了与消费类嵌入式系统（例如汽车，WebTV和蜂窝电话）的实时操作系统（RTOS）服务的设计和实现有关的问题。由于这些设备是批量生产的，因此降低生产成本非常重要，这意味着RTOS服务必须高效才能在这些设备中使用低成本硬件。本文探讨了基本RTOS服务（任务调度，同步和通信）的优化技术，以满足嵌入式系统的需求。首先，动态调度程序（如最早截止期限的第一时间（EDF））具有较高的处理器利用率，但会产生较高的运行时开销，而静态调度程序（如速率单调（RM））则相反。我们设计了结合了EDF和RM的静态/动态（CSD）调度程序，以提供与RM相当的运行时开销以及与EDF相当的利用率。其次，对OO编程的越来越多的使用已使高效的同步对于嵌入式系统非常重要。在OO多任务环境中，必须通过信号量保护对对象的访问，以确保相互排斥。我们提出了一种新的信号量实现方案，该方案通过重新安排线程的使用以最大程度地减少阻塞，从而在大多数情况下为每个锁定操作节省一个上下文切换。第三，具有Internet连接性的嵌入式设备需要有效处理网络数据。我们提出一种协议体系结构，以减少音频和视频消息的接收开销。该架构通过安全地绕过多个协议层（有益于短音频消息）来减少I-cache丢失，并且实时消息数据仅被复制一次而无需任何硬件支持（有益于长视频消息）。最后，嵌入局域网（LAN）的嵌入式系统需要适当的LAN消息调度。控制器局域网（CAN）是在汽车应用中流行的LAN。对于纯CAN来说，纯EDF调度是不可行的，因为开销不可接受，而最后期限单调（DM）调度是可行的，但网络利用率较低。我们提出了可行的混合流量调度器（MTS），它使用量化的期限将EDF和DM结合起来，以提供比DM更高的利用率。使用这些优化，我们构建并评估了RTOS，该RTOS为程序员提供了丰富的服务，并满足了嵌入式系统的效率/成本要求。

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