317 research outputs found
Real-Time Containers: A Survey
No full textContainer-based virtualization has gained a significant importance in a deployment of software applications in cloud-based environments. The technology fully relies on operating system features and does not require a virtualization layer (hypervisor) that introduces a performance degradation. Container-based virtualization allows to co-locate multiple isolated containers on a single computation node as well as to decompose an application into multiple containers distributed among several hosts (e.g., in fog computing layer). Such a technology seems very promising in other domains as well, e.g., in industrial automation, automotive, and aviation industry where mixed criticality containerized applications from various vendors can be co-located on shared resources.
However, such industrial domains often require real-time behavior (i.e, a capability to meet predefined deadlines). These capabilities are not fully supported by the container-based virtualization yet. In this work, we provide a systematic literature survey study that summarizes the effort of the research community on bringing real-time properties in container-based virtualization. We categorize existing work into main research areas and identify possible immature points of the technology
Real-time containers : A survey
No full textContainer-based virtualization has gained a significant importance in a deployment of software applications in cloud-based environments. The technology fully relies on operating system features and does not require a virtualization layer (hypervisor) that introduces a performance degradation. Container-based virtualization allows to co-locate multiple isolated containers on a single computation node as well as to decompose an application into multiple containers distributed among several hosts (e.g., in fog computing layer). Such a technology seems very promising in other domains as well, e.g., in industrial automation, automotive, and aviation industry where mixed criticality containerized applications from various vendors can be co-located on shared resources. However, such industrial domains often require real-time behavior (i.e, a capability to meet predefined deadlines). These capabilities are not fully supported by the container-based virtualization yet. In this work, we provide a systematic literature survey study that summarizes the effort of the research community on bringing real-time properties in container-based virtualization. We categorize existing work into main research areas and identify possible immature points of the technology. © Václav Struhár, Moris Behnam, Mohammad Ashjaei, and Alessandro V. Papadopoulos; licensed under Creative Commons License CC-BY 2nd Workshop on Fog Computing and the IoT (Fog-IoT 2020).</p
Per processor spin-based protocols for multiprocessor real-time systems
No full textThis paper investigates preemptive spin-based global resource sharing protocols for resource-constrained real-time embedded multi-core systems based on partitioned fixed-priority preemptive scheduling. We present preemptive spin-based protocols that feature (i) an increased schedulability ratio of task sets and reduced response jitter of tasks compared to the classical non-preemptive spin-based protocol, (ii) similar memory requirements for the administration of waiting tasks as for the non-preemptive protocol whilst only causing (iii) a minimal increase of the minimal number of required stacks per core from one to at most two, and (iv) strong progress guarantees to tasks. We complement these protocols with a unified worst-case response time analysis that specializes to the classical analysis for the non-preemptive protocol. The paper includes a comparative evaluation of the preemptive protocols and the non-preemptive protocol based on synthetic data
Bayesian methods for addressing long-standing problems in associative learning: The case of PREE
No full textThe author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: Joaquin Moris was funded with a Juan de la Cierva Postdoctoral grant. This research was supported by grants PSI2013-43516-R and PSI2016-78818-R of the Spanish Ministry of Economy and Competitiveness, and grant IT955-16 of the Basque Government
Hierarchical Real Time Scheduling and Synchronization
No full text The Hierarchical Scheduling Framework (HSF) has been introduced to enable compositional schedulability analysis and execution of embedded software systems with real-time constraints. In this thesis, we consider a system consisting of a number of semi-independent components called subsystems, and these subsystems are allowed to share logical resources. The HSF provides CPU-time to the subsystems and it guarantees that the individual subsystems respect their allocated CPU budgets. However, if subsystems are allowed to share logical resources, extra complexity with respect to analysis and run-time mechanisms is introduced. In this thesis we address three issues related to hierarchical scheduling of semi-independent subsystems. In the first part, we investigate the feasibility of implementing the hierarchical scheduling framework in a commercial operating system, and we present the detailed figures of various key properties with respect to the overhead of the implementation. In the second part, we studied the problem of supporting shared resources in a hierarchical scheduling framework and we propose two different solutions to support resource sharing. The first proposed solution is called SIRAP, a synchronization protocol for resource sharing in hierarchically scheduled open real-time systems, and the second solution is an enhanced overrun mechanism. In the third part, we present a resource efficient approach to minimize system load (i.e., the collective CPU requirements to guarantee the schedulability of hierarchically scheduled subsystems). Our work is motivated from a tradeoff between reducing resource locking times and reducing system load. We formulate an optimization problem that determines the resource locking times of each individual subsystem with the goal of minimizing the system load subject to system schedulability. We present linear complexity algorithms to find an optimal solution to the problem, and we prove their correctness
Synchronization Protocols for a Compositional Real-Time Scheduling Framework
No full textIn this thesis we propose techniques to simplify the integration of subsystems while minimizing the overall amount of CPU resources needed to guarantee the schedulability of real-time tasks. In addition, we provide solutions to the problem of allowing for the use of logical resources requiring mutual exclusion. The contribution of the thesis is presented in three parts. In the first part, we propose a synchronization protocol, called SIRAP, to facilitate sharing of logical resources in a hierarchical scheduling framework. In addition, we extend an existing synchronization protocol, called HSRP, such that each subsystem can be developed independently. The performance of the proposed protocols is evaluated by extensive simulations. In the second part, we present an efficient schedulability analysis that exploits the lower scheduling overhead introduced by each of the proposed protocols. Finally, in the third part, we propose new methods and algorithms that find the optimal system parameters (e.g., optimal resource ceiling), that minimize the amount of CPU resources required to ensure schedulability, when using the proposed synchronization protocols in a hierarchical scheduling framework. The motivation of this work comes from an emerging industrial trend in embedded software systems development to integrate multiple applications (subsystems) on a small number of processors. The purpose of this integration is to reduce the hardware related costs as well as the communication complexity between processors. In this setting a large number of industrial applications face the problem of preserving their real-time properties after their integration onto a single processor. In addition, temporal isolation between the applications during runtime may be required to prevent failure propagation between different applications. Specifically, we propose a hierarchical scheduling framework that allows for a simplified integration of subsystems. The framework preserves the essential temporal characteristics of the subsystems, both when running in isolation as well as when they are integrated with other subsystems. In this thesis, we assume a model where a system consists of a number of subsystems. The subsystems can interact with each other using shared logical resources. The framework ensures that the individual subsystem respects its allocated share of the processor. The difficulty lies in allowing two or more subsystems to share logical resources, which introduces an additional complexity in the schedulability analysis and also increases the system load
Real-Time Control and Scheduling Co-Design for Efficient Jitter Handling
No full textReal-time control algorithms are designed based on thecharacteristics of the controlled plants and they require goodperformance without delays. However, digital control implementationtypically introduces delays and jitters due to insufficient CPUprocessing power and the limitations of the real-time schedulingmethod used. This can degrade the system performance or even make itunstable.In this paper we propose an integrated approach for control designand real-time scheduling, suitable for both discrete-time andcontinuous-time controllers. It guarantees system performance byaccepting a certain minimum value of jitter for control tasks andfeasibly schedules them together with other tasks in the system.Results from comparison with other approaches from real-time andcontrol theory domains underline the effectiveness of our method.</p
Subsystem-Interface Generation in the Presence of Shared Resources
No full textThe Hierarchical Scheduling Framework (HSF) has been introduced as a design-time framework enabling compositional schedulability analysis of embedded software systems with real-time properties. However, supporting resource sharing in HSF is a major challenge, since it increases the amount of the CPU resources required to guarantee the schedulability of the hard real time tasks and decreases the composability at the system level. In this paper, we discuss and identify the key parameters of a compositional framework called the bounded-delay resource open environment (BROE) server to support global resource sharing, that have a great effect on how the framework will utilize CPU resources. Furthermore, we provide an algorithm, that has a pseudo-polynomial complexity, to evaluate the optimal setting for the BROE server. In addition, we provide a polynomial-time approximation algorithm for generating near-optimal setting for the BROE server. The performance of the BROE server, as well as the efficiency of the approximated algorithm, is evaluated by the means of simulation analysis.</p
Real-Time Control Design for Flexible Scheduling using Jitter Margin
No full textReal-time control algorithms are designed based on the characteristics of the controlled plants and they require good performance without delays. However, digital control implementation typically introduces delays and jitters due to insufficient CPU processing power and the limitations of the real-time scheduling method used. This can degrade the system performance or even make it unstable. In this paper we propose an integrated approach for control design and real-time scheduling, suitable for both discrete-time and continuous-time controllers. It guarantees system performance by accepting a certain minimum value of jitter for control tasks and feasibly schedules them together with other tasks in the system. Results from comparison with other approaches from real-time and control theory domains underline the effectiveness of our method.
Selected papers presented at the 26th International Conference on Real-Time and Network Systems (RTNS 2018)
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