Real-time capabilities of Linux RTAI

Arm, Jakub; Bradáč, Zdeněk; Kaczmarczyk, Václav

doi:10.1016/j.ifacol.2016.12.080

Cited by 13 publications

(9 citation statements)

References 2 publications

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“…Arm et al 25 analyzed the real-time capabilities for the RTAI Linux real-time extension, which is also a dual kernel approach, on LinuxCNC. Brown and Martin 24 evaluated three cases, namely the performance of a baseline Linux kernel, the performance of the same kernel with the PREEMPT_RT patches, and the performance of this kernel with the Xenomai patches, by measuring the latency interrupt and the jitter of a periodic task.…”

Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

“…Unlike the previously mentioned works, 24,25,27 in this work real-time performance with native Linux code has been achieved without applying patches for real-time extensions. FIQ is the highest priority interrupt request in an ARM CPU and, while restricted to this specific architecture, it is technically very similar to the nonmaskable interrupt signal available in other architectures.…”

Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

“…They concluded that in the kernel space, the native Linux code has better performance for the 95% hard real-time category and Xenomai is the best for the 100% hard real-time category. Arm et al 25 analyzed the real-time capabilities for the RTAI Linux real-time extension, which is also a dual kernel approach, on LinuxCNC. In industrial applications, the Lin-uxCNC is offered to operate Computer Numerical Control machines.…”

Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

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Real‐time performance assessment using fast interrupt request on a standard Linux kernel

Souza

Freitas

Jimenez

et al. 2020

Engineering Reports

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This article presents the use of ARM's fast interrupt request (FIQ) to accomplish better jitter performance on real-time drivers without using patches for real-time extensions on the native Linux kernel code. Writing an FIQ interrupt handler is challenging due to the lack of Linux kernel support and the need to avoid page faults exception during its execution. We investigate and evaluate a mechanism that employs static mapping for peripherals and changes on the Linux kernel code to allow the FIQ interrupt handler to be written in the C language. Furthermore, the FIQ performance was evaluated by comparing it with a timer Interrupt Request on Linux PREEMPT-RT in full CONFIG_PREEMPT_RT mode. Both were applied on a Linux driver for data acquisition of a pipeline inspection gauge system. Results show that the FIQ approach was able to reduce in 97.49% the interrupt jitter and, as a result, allowed an increase in the data acquisition frequency from 1024 Hz to 2048 Hz, showing that the FIQ approach can be considered for real-time applications without resorting to real-time extensions. K E Y W O R D Sembedded software, FIQ interrupt, jitter, Linux kernel, pipeline inspection gauge, real-time driver INTRODUCTIONReal-time applications are widely employed by several industrial sectors, such as robotics, 1 aerospace, 2 and automotive, 3 using real-time operating systems (RTOSs). The timing correctness of systems is traditionally guaranteed by the worst-case execution time (WCET) analysis. The purpose of this analysis is to determine if the system meets its real-time constraints, that is, short response time of a task, short execution time of the interruption, and among others. Usually, the WCET analysis is mandatory for hard-real time systems, 4 however, other real-time applications can be less demanding regarding accomplishments of the real-time constraints, and their performance can be evaluated according to their latency and jitter. 5 Jitter caused by both hardware (caches and pipelines) and software effects (disabled interrupts and mechanisms for synchronizing processes) is typically in the order of microseconds, which can be long enough to affect a real-time application. For instance, in real-time control systems, feedback control loops are implemented as execution of periodic tasks. The impact of jitter on such application is typically analyzed to ensure control system's stability. [6][7][8] Latency is defined as the time elapsed between the occurrence of an external event and the correct reaction to thatThis is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

Section: Linux Kernel In Embedded Systemsmentioning

confidence: 99%

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Real‐time performance assessment using fast interrupt request on a standard Linux kernel

Souza

Freitas

Jimenez

et al. 2020

Engineering Reports

View full text Add to dashboard Cite

show abstract

“…In this approach, the standard Linux has the lowest priority and would only run if there are no tasks available for the real-time kernel. Two dual-kernel approach projects are currently available, namely Xenomai and RTAI [14,21,22]. Both Xenomai and RTAI are more accurate in meeting hard real-time deadlines with lower standard deviations and offers API for the real-time driver model (RTDM) [23].…”

Section: Real-time Embedded Linux Approachesmentioning

confidence: 99%

Open Embedded Real-time Controllers for Industrial Distributed Control Systems

2019

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This paper presents design details adopting open embedded systems (OES) as real-time controllers in industrial distributed control systems. OES minimize development cost and enhance portability while addressing widely known shortcomings of their proprietary counterparts. These shortcomings include the black box method of distribution which hinders integration to more complex systems. However, OES are highly dependent on the compatibility of each software components and essential benchmarking is required to ensure that the system can satisfy hard real-time constraints. To address these issues and the notion that OES will find broader distributed control applications, we provide detailed procedures in realizing OES based on an open source real-time operating system on various low-cost open embedded platforms. Their performance was evaluated and compared in terms of periodicity and schedulability, task synchronization, and interrupt response time, which are crucial metrics to determine stability and reliability of real-time controllers. Practical implementations, including the modernization of a multi-axis industrial robot controller, are described clearly to serve as a comprehensive reference on the integration of OES in industrial distributed control systems.

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“…From down to top, the structure consists of a driver layer, an operating system layer (uC/OS-Ⅱ), a graphical interface system (MiniGUI) and an application layer. The driver layer includes a TFT LCD driver, an ADC driver, an encoder driver, a keyboard driver, a flash memory driver and a real-time clock driver, while the application layer contains functional modules like signal analysis, man-machine interface and data storage [20][21][22][23].…”

Section: Software Designmentioning

confidence: 99%

Development and Application of a Modular Automobile Wheel Measuring Instrument

Yuan¹

2019

I2M

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This paper designs a portable instrument for automobile wheel measurement, and details the measurement method and the hardware and software structures. Taking LPC2294 as its microcontroller, the instrument runs on the operating system uC/OS-II, adopts the graphical interface system MiniGUI, and uses multiple sensors. The main functions of the instrument include the measurement of the runout and press-fit depth and the harmonic analysis. The modular structure makes the instrument easy to move and carry. The instrument can be applied to measure various types of automobile wheels and enjoys a broad application potential.

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Real-time capabilities of Linux RTAI

Cited by 13 publications

References 2 publications

Real‐time performance assessment using fast interrupt request on a standard Linux kernel

Real‐time performance assessment using fast interrupt request on a standard Linux kernel

Open Embedded Real-time Controllers for Industrial Distributed Control Systems

Development and Application of a Modular Automobile Wheel Measuring Instrument

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