【作者】 徐超；

【导师】 刘云生；

【作者基本信息】 华中科技大学 ， 计算机软件与理论， 2004， 硕士

【摘要】 实时系统不仅要求吞吐率高,还要求系统的所有组件都是可靠且可预测的。通常的实时系统由底层硬件、RTOS和上层应用三部分组成。应用层依赖于操作系统,虽然有一些验证应用是否满足时限要求的算法,但这些方法都是基于操作系统是实时的基础上的。底层硬件也要求是具有确定性的,但是一些新的硬件技术是基于提高系统总体平均效率的统计学思想上开发的,有可能同实时系统要求的可预测性相违背。RTOS负责管理硬件资源,并为上层应用提供系统功能接口和开发环境。要确定一个操作系统是实时的,需要分析系统的体系结构和实现技术。首先分析实时系统的特点和要求,以此推出判断一个操作系统是实时操作系统的必备条件。实时系统要求RTOS的系统行为具有实时性和可预测性。以分析GPOS中采用的主要技术是否适用于RTOS为主线,研究为了达到实时性和可预测性,系统体系结构、任务模式、内存管理和中断机制等实现技术应如何改进。以此作为RTOS技术评价的标准。RTOS还应该为应用开发提供丰富的应用程序接口和良好的开发环境。验证一个RTOS是否具有良好的实时性能,需要对相关性能指标进行实际的测试。RTOS实时性能指标包括一系列系统底层作业的时间特性,主要包括进程管理、中断管理、IPC机制、文件系统、网络协议栈等功能模块的实时性能指标测试。仅同中断处理相关的性能指标就有中断延迟、中断分派延迟、中断优先级和中断嵌套、最大可响应中断频率等几项。RTOS性能测试的设计思想是:定义合理的测试项目,设计标准化的测试过程。力求达到全面、系统、标准、精确,测试结果可验证、可比较。本文按上述内容展开论述,并对自主开发的嵌入式实时操作系统ARTs-OS实施相应的技术分析和测试。更多还原

【Abstract】 A system does not only need to have a high throughput but all its components need to be reliable and predictable. A generic real-time system is composed of three levels: the hardware, the operating system and the application. At application level, the software relies on the operating system. Several methods can be used to verify whether or not an application can meet deadline requirements. However this type of analysis is based on the assumption that the operating system is a real-time system. The underlying hardware needs to be deterministic. Some technology of hardware is base on the statistics, which is to improve the average performance, so this may introduce non real-time responses. RTOS manage the hardware resources, and provide API and development tools for application.To identify an OS is a RTOS, it’s necessary to analyze the system architecture and realization technology. The first step is to study the requirement of real-time system. This induces the minimum requirements of a RTOS. The next step is to examine techniques that can be found in General Purpose Operating Systems (GPOS) and explain why they can or cannot be used in real-time operating systems. These techniques include OS structures, task-mode, memory management, and interrupt technologies. All this above will be used as the reference of RTOS technical evaluation. And also, a good RTOS should provide sufficient API and friendly development environment for application development. Another section evaluates the performance of RTOS. The evaluation is based upon a series of practical tests. The testing measures low-level operations of a RTOS including Task Management, Memory Management, Interrupt, IPC Mechanism, File System, and Network Stack. Interrupt as an example, there are 4 main features should be studied and tested: Interrupt Latency, Interrupt Dispatch Latency, Interrupt Priority & Nest, and Maximum Sustainable Interrupt Frequency. The design idea of these tests is defining rational test items and designing standardization test procedure, ensuring the test results can be validated and compared.更多还原