Handset manufacturers and network equipment providers are being pressured to deliver new, unique solutions and services. Such demands cause software requirements to outstrip the capabilities of aging real-time operating systems, making way for Linux to become the strategic end-to-end platform used in building next generation communications infrastructure and mobile and wireless devices.

MontaVista Contribution

MontaVista Software has helped evolve native, hard real-time developments to the Linux kernel, thus moving closer to achieving interrupt response characteristics previously attributed to specialized and proprietary, commercial real-time operating systems.

In 1999, MontaVista introduced the MontaVista Preemptible Linux Kernel, later adopted as a mainstream Linux feature, that leveraged the spin-locks that protect critical regions in the Linux Symmetric Multi-Processing (SMP) kernel. In 2000, MontaVista added APIs to support CPU affinity in multi-processor systems into the Open Source community O(1) scheduler. In 2002, MontaVista introduced High Resolution Timers (HRT) for systems and applications that require better timing resolution than the standard Linux 10 millisecond timebase can provide, providing increased control over real-time application behavior.

MontaVista's most recent work further enhances the community-established real-time foundation, which pushes the Linux kernel's performance and predictability. Today's real-time milestone further advances the kernel toward predictable response times, making this the last hurdle in evolving a hard real-time Linux kernel.

The native, hard real-time developments, jointly developed with the Open Source community, will be included as a standard feature in next generation MontaVista products.

Here is a look at how the real-time responsiveness in Linux has progressed in the last 5 years:

Real-Time Response

Real-time requirements vary between markets. The bottom section shows typical real-time requirements of various vertical segments. Most real-time applications have response requirements from >5000 microseconds to <10 microseconds. The gray area shows the section of the total embedded real-time market that is satisfied at a given response level. MontaVista Linux has made dramatic improvement in the real-time performance in native Linux, as represented by the circles.

Open Source Contributions

MontaVista Software open sourced a working prototype of the real-time kernel in October 2004. Since then, Ingo Molnar has adopted and taken over maintenance of this project. MontaVista Software has continuously contributed to this project. On June 8, 2005, MontaVista open sourced an enhancement to the interrupt sub-system facilitating deterministic interrupt response. This enhancement was subsequently incorporated into the preempt real-time project maintained by Molnar.

	Some key contributors to the overall real-time effort include, in alphabetical order:
	Ingo Molnar (maintainer) Sven Dietrich K. R. Foley Thomas Gleixner Gene Heskett Bill Huey Paul McKenney	Esben Nielsen Nick Piggin Lee Revell Steven Rostedt Michal Schmidt Daniel Walker Karsten Wiese