Real-Time Linux Project
MontaVista Software has launched an initiative to gain orders of magnitude improvement in the real-time responsiveness of Linux, by extending Linux to achieve hard real-time performance.
MontaVista is hosting the “Open Source Real-Time Linux Project” and has contributed a reference implementation based on the company’s recent work in the area of real-time Linux determinism.
“Extremely fast real-time capability is the final barrier to comprehensive implementation of Linux in a wide range of devices,” said James Ready, president and CEO, MontaVista Software. “Our strategy has always been to drive native real-time improvements in Linux itself, and to open the process to as large a developer audience as possible. We want Linux to achieve and even exceed the responsiveness attributes of proprietary kernel products, while continuing to provide all the benefits of Open Source. With hard real-time capabilities, Linux is set to assume the role of a universal platform.”
In the past, proponents of proprietary and closed-source platforms have suggested that Linux can never offer sufficient responsiveness to displace Real-Time Operating Systems (RTOSes) in key embedded and communications applications. With this project the final barrier can be overcome and the proprietary RTOS will swiftly become dispensable — Linux will be set to subsume many markets that were previously the exclusive domain of the RTOS.
“In our prototypes we are able to achieve hundred-fold improvement in responsiveness, with worst case latencies down to tens of microseconds,” said Kevin Morgan, vice president, Engineering, MontaVista Software. “In initiating this project, MontaVista’s goal is to advance the technology even further for the benefit of all users; to rally other developers in the Linux community to help achieve the goal; and to encourage other vendors to support a unified industry standard for hard real-time Linux.”
New Markets, New Applications
This initiative will grow the total addressable market for Linux by enabling the operating system to meet the hard real-time requirements of embedded and communications applications. For example, Linux is used today in many communications applications, such as the management plane for mobile infrastructure. With these improvements in real-time performance, Linux will become suitable for use in the data plane for line-card applications and IP-packet processing. In addition, these enhancements will help push Linux into the mid-tier “feature phones,” by eliminating the need for an RTOS running on a dedicated baseband processor. Linux, with carrier-grade features, power management and hard real-time performance, can now be used as an end-to-end solution across the network. The benefits of a single OS across all network elements will be a significant advantage to network equipment providers, operators and handset OEMs.
“Linux continues to gain share in the mobile phone industry, and the success of this initiative will open up more potential markets,” said Stacey Quandt, senior business analyst, Robert Frances Group. “Uses for hard real-time Linux include mobile handsets and their communication networks, as well as various Internet infrastructure applications.”
A recent industry report from Venture Development Corporation (VDC) claims that limited real-time performance is one of the concerns of embedded developers who are evaluating Linux for future projects (Linux in the Embedded Systems Market, 2004). The same report indicates that in embedded projects where real-time is an issue, 66 percent require interrupt response times that range from 100 to less than 5 microseconds. Enabling Linux to achieve these response time requirements is a key goal of this project.
“MontaVista Software continues to drive Linux beyond the traditional Linux markets, into new market segments such as the mobile handset,” commented Ward Pitkin, software product manager, Wireless Terminals Business Unit, Texas Instruments. “With the introduction of real-time technology for Linux, as well as the Open Source project, the possibilities are endless for what Linux will foster in these new markets.”
Open Source Project
This project builds on MontaVista’s record of technical innovation and past real-time contributions including the preemptible kernel technology, which was accepted into the 2.6 Linux kernel; the first fixed overhead real-time scheduler for Linux (design attributes of which were incorporated into the O(1) scheduler); and high resolution time management for Linux.
The goal of this project is to deliver performance and deterministic real-time responsiveness that is comparable to that of other commercial and proprietary RTOSes. MontaVista expects to lower Linux task preemption latency (worst case) from a range of one to tens of milliseconds, down to tens of microseconds, for time-critical applications. This would be an improvement of at least two orders of magnitude in Linux responsiveness.
The project targets the following specific technical goals:
— To allow application or system designers to impose reliable priority response on Interrupt handling
— To utilize priority inheritance mutexes to manage access to data protected by critical sections in the kernel
— To provision priority management throughout all kernel subsystems
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