Application-specic service technologies for commodity operating systems in real-time environments

In order to eliminate the costs of proprietary systems and special purpose hardware, many real-time and em-bedded computing platforms are being built on commod-ity operating systems and generic hardware. Unfortunately, many such systems are ill-suited to the low-latency and predictable timing requirements of real-time applications. This paper, therefore, focuses on application-specific ser-vice technologies for low-cost commodity operating sys-tems and hardware, so that real-time service guarantees can be met. We describe contrasting methods to deploy rst-class services on commodity systems, that are dispatched with low latency and execute asynchronously according to bounds on CPU, memory and I/O device usage. Specifically, we present a “user-level sandboxing ” (ULS) mechanism, that relies on hardware protection to isolate application-specific services from the core kernel. This approach is compared with a hybrid language and run-time protection scheme called “SafeX”, that allows untrusted services to be dynamically linked and loaded into a base kernel. SafeX and ULS have been implemented on commodity Linux sys-tems. Experimental results show that both approaches are capable of reducing service violations (and, hence, better qualities of service) for real-time tasks, compared to tradi-tional user-level methods of service deployment in process-private address spaces. ULS imposes minimal additional overheads on service dispatch latency compared to SafeX, with the advantage that it does not require application-specific services to execute in the trusted kernel domain. 1