Computer systems that are required to respond immediately to specific events, such as control systems in cars, airplanes, or home security systems, are based on platforms that are often referred to as "real-time operating systems" (RTOSs). However, as embedded systems make their way into many other devices, and processors generally become faster, the boundary between "real-time" and "conventional" operating systems becomes somewhat blurred, as the responsiveness requirements differ from application to application. Accordingly, there are a variety of approaches to develop "real-time" Linux. E.g., RTLinux adds a microkernel that developers can use to write real-time applications that require less than one millisecond interrupt latencies, while regular applications continue to be run by standard Linux.
Other companies like Monta Vista and Timesys take the approach of improving the performance of the Linux kernel to achieve interrupt response times below five milliseconds, which effectively makes it an RTOS. A third approach, exemplified by LynxOS, extends a real-time operating system to run Linux applications.
A real time version of Linux developed by the Open Source Real-Time Linux Project shows interrupt response times down to 100 microseconds, which was previously only achieved by proprietary real time operating systems. ItÂ’s responsiveness is 30 times faster than that of the 2.6.12.3 Linux kernel, and 100 times faster than the responsiveness of the 2.6.10 kernel. The open source project developed the real-time version for the x86 platform, and MontaVista ported it to the ARM, PowerPC, and MIPS architectures.
Demand for flexible, open-source RTOSs is strong, with applications ranging from mobile phones and other wireless devices to network equipment. This is a fast growing area.
