On static WCET analysis vs. run-time monitoring of execution time

Summary form only given. Dynamic, distributed, real-time control systems control a widely varying environment, are made up of application programs that are dispersed among loosely-coupled computers, and must control the environment in a timely manner. The environment determines the number of threats; thus, it is difficult to determine the range of the workload at design time using static worst-case execution time analysis. While a system is lightly loaded, it is wasteful to reserve resources for the heaviest load. Likewise, it is also possible that the load will increase higher than the assumed worst case. A system that has a preset number of resources reserved to it is no longer guaranteed to meet its deadlines under such conditions. In order to ensure that such applications meet their real-time requirements, a mechanism is required to monitor and maintain the real-time quality of service (QoS): a QoS manager, which monitors the processing timing (latency) and resource usage of a distributed real-time system, forecasts, detects and diagnoses violations of the timing constraints, and requests more or fewer resources to maintain the desired timing characteristics. To enable better control over the system, the goals are as follows: 1) Gather detailed information about antiair warfare and air-traffic control application domains and employ it in the creation of a distributed real-time sensing and visualization testbed for air-traffic control. 2) Identify mathematical relationships among independent and dependent variables, such as performance and fault tolerance vs. resource usage, and security vs. performance. 3) Uncover new techniques for ensuring performance, fault tolerance, and security by optimizing the variables under the constraints of resource availability and user requirements.