MontaVista Enhances Linux Kernel for Real-Time Performance

MontaVista Software Inc., developer of the Hard HatTM Linux® operating system for embedded applications, announced plans to offer an array of real-time performance options for its embedded Linux distribution. To address the range of requirements for real-time responsiveness and determinism, MontaVista will enhance the already good performance of the standard Linux kernel for more predictable 'soft' real-time response and partner with real-time Linux leader FSMLabs to offer an RTLinuxTM accelerator for 'hard' real-time applications. Building upon a 'one hundred percent pure Linux' base, MontaVista is characterizing driver-level and user process response characteristics in the Linux kernel and engineering a range of improvements to enable guaranteed single-millisecond response times.

All such enhancements will be released back to the open source community under the Gnu Public License. For the ultimate in deterministic Linux, MontaVista will offer hard real-time response with the addition of FSMLabs' RTLinux real-time acceleration extension. Real-time systems are variously termed 'hard' and 'soft'. Hard real-time behavior entails a guaranteed maximum response time to stimuli (typically interrupt I/O), independent of system load.

Soft real-time involves application or system response to stimuli in a time-sensitive context, but without guarantees of time-liness. No particular time resolution is implied by hard or soft real-time requirements, but most so-called real-time systems operate on time-scales in the sub-millisecond or even microsecond range. Applications with hard real-time deadlines include signal processing and industrial control, while there exists a very broad range of applications with soft real-time requirements, including data communications and most Internet-related embedded systems. Technical Details MontaVista improvements in Linux soft real-time performance include reduction in worst-case interrupt blocking times, development of a fixed-priority real-time scheduler with constant dispatch overhead, and methods for dramatically improving process-level response timings. RTLinux acts as a hard real-time accelerator for Hard Hat Linux, equipping the standard Linux kernel with POSIX (IEEE 1003.1c) thread and signal handlers that execute predictably, with latencies and timing limited only by the resident hardware. RTLinux real-time threads and signal handlers are decoupled from standard Linux kernel so that non-real-time Linux functions do not delay real-time processing, and can communicate with and access facilities of standard Linux. The RTLinux Accelerator for Hard Hat Linux currently supports uniprocessor and SMP x86 and PowerPCTM microprocessor architectures.