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Testing farm pushes real-time Linux into the mainstream

Nov 22, 2010 — by Eric Brown — from the LinuxDevices Archive — 9 views

OSADL, which has been overseeing real-time Linux (RTL) development patches to the Linux kernel, announced a “quality assurance testing farm” where manufacturers can test a variety of RTL systems under simulated production conditions. The multi-platform test center aims to prove RTL as a capable, and more flexible, alternative to real-time operating systems (RTOSes).

OSADL (Open Source Automation Development Lab) coordinates the development of open source projects in the areas of embedded and industrial design, including projects focused on real-time and safety critical Linux, I/O framework, real-time Ethernet, and special automation-related drivers for the Linux kernel. In May of this year, OSADL became a Silver member of the Linux Foundation.

Since its merger with the Real-Time Linux Foundation (RTLF) early last year, OSADL has also regularly released "Latest Stable" industrial real-time Linux kernels based on its PREEMPT_RT patch series. In February, OSADL released Kernel, based on Linux 2.6.31, which is still recommended by OSADL as the latest stable version.

The new assurance farm combines a series of OSADL test racks, which have been used to test the PREEMPT_RT-patched Linux kernels before they are released as latest stable. Developed by RTL project leader and embedded Linux pioneer Thomas Gleixner, the racks, one of which is pictured at left, provide a framework for testing for required RTL stability and expected real-time performance, including latency tests, says OSADL.

The assurance farm is billed as a major step in OSADL's goal of getting real-time Linux officially certified as both a high-performance real-time OS and a "safe" RTOS, as part of the group's Safety Critical Linux project. The farm aims to prove that Linux is now a bonafide real-time operating system, providing similar performance as other RTOSes, but with much broader hardware support, along with features such as 64-bit support, multi-processing, and virtualization.

RTL is required for Linux to enter many mission-critical telecom, military, healthcare, music recording, and financial trading applications. Most of these are embedded applications that still use RTOSes such as VxWorks or QNX.

In addition, RTL "has helped to investigate, localize, and fix a number of difficult to find kernel problems and contributed to improve the multiprocessing performance of Linux," says OSADL.

Real-time Linux provides for real-time determinism with guaranteed hard timing deadlines. RTL requires the coordination of numerous components, including a scheduler that can react in the required time "irrespective of the number of waiting tasks," says OSADL. Additional components are said to prevent priority inversion, make the kernel and IRQ handlers pre-emptible, make waiting loops interruptible, and provide high-resolution timers. (For more technical background on RTL, see our earlier coverage, here and here.)

Down on the farm

The initial OSADL quality assurance (QA) farm for real-time Linux offers systems based on x86, PowerPC, ARM, and MIPS architectures, with some available in both 32-bit and 64-bit variants, says OSADL. The x86 test systems, meanwhile, are said to be available as uniprocessor and multiprocessor systems.

Tests continuously monitor combined and individual wakeup and timer latency, says OSADL. In addition, every six hours, a six-hour cyclic test records single measurements to create latency histograms that are posted online, says OSADL. Initially, the test runs under idle conditions for two hours, and during the remaining four hours, a defined memory, I/O, network, and file system load scenario is created.

Two of the systems are equipped with an additional Ethernet adapter connected to the standard Ethernet adapter via a crossover cable. The adapters run a UDP network server and client, to form a generic implementation of a real-time Ethernet link. Two other systems are equipped with PCI communication cards that can run a variety of real-time Ethernet protocols as master and slave, says the organization.

Future assurance farm plans call for adding more computer systems with different processors, controllers, and industrial subsystems, says OSADL.

Stated Carsten Emde, general manager of OSADL, "As far as we know, this is the first QA farm of its kind. We are convinced that it represents an important step towards a generally accepted and validated real-time operating system for the automation industry."


The OSADL teal-time quality assurance farm is now open for business, although it appears that OSADL membership is required. More information on the OSADL teal-time QA farm may be found here.

The OSADL QA farm will be showcased at this year's SPS/IPC/Drives conference in Nuremberg, Germany, hall 8, #509, from Nov. 23 to 25.

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