Soft real-time application execution with dynamic quality of service assurance (original) (raw)

2002

https://doi.org/10.1109/IWQOS.1998.675233

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An Approach to Advance Real-Time Os Services with Soft-Error

International Journal of Computer and Electrical Engineering, 2011

the rises of RTOSs have evolved from single-use specialized systems to a wide of more general purpose Operating Systems (such as real-time variants of Open Source Operation System. These-days, numbers of critical applications that have stringent real-time constraint are placed and run in an environment with Real-Time operating system (RTOS). The provided services of RTOSs are subject to faults that affect both functional and timing of Tasks which are running based on RTOS. In this paper, we try to evaluate and analyze robustness of services due to soft-errors in two proposed architecture of RTOS which are (SW-RTOS and HW/SW-RTOS). Accordingly, we propose for an architecture which provides more robust services in term of soft-error. Real-Time Operating System (RTOS) users desire predictable response time at an affordable cost, due to this demand Hardware/Software Real-Time Operating Systems (HW/SW-RTOS) appeared. This paper analyzes the impact of softerrors in real-time systems running applications under purely Software RTOS versus HW/SW-RTOS. The proposed model is used to evaluate robustness of services like scheduling, synchronization time management and memory management and inter process communication in Software based RTOS and HW/SW-RTOS. Experimental results show HW/SW-RTOS provide more robust services in term of soft-error against purely software based RTOS.

A cloud middleware for assuring performance and high availability of soft real-time applications

Journal of Systems Architecture, 2014

Applications are increasingly being deployed in the cloud due to benefits stemming from economy of scale, scalability, flexibility and utility-based pricing model. Although most cloud-based applications have hitherto been enterprise-style, there is an emerging need for hosting real-time streaming applications in the cloud that demand both high availability and low latency. Contemporary cloud computing research has seldom focused on solutions that provide both high availability and real-time assurance to these applications in a way that also optimizes resource consumption in data centers, which is a key consideration for cloud providers. This paper makes three contributions to address this dual challenge. First, it describes an architecture for a fault-tolerant framework that can be used to automatically deploy replicas of virtual machines in data centers in a way that optimizes resources while assuring availability and responsiveness. Second, it describes the design of a pluggable framework within the fault-tolerant architecture that enables plugging in different placement algorithms for VM replica deployment. Third, it

Transport Services for Soft Real-Time Applications in IP Networks

In recent years, Internet and IP technologies have made inroads into almost every communication market ranging from best-effort services such as email and Web, to soft real-time applications such as VoIP, IPTV, and video. However, providing a transport service over IP that meets the timeliness and availability requirements of soft real-time applications has turned out to be a complex task. Although network solutions such as IntServ, DiffServ, MPLS, and VRRP have been suggested, these solutions many times fail to provide a transport service for soft real-time applications end to end. Additionally, they have so far only been modestly deployed. In light of this, this thesis considers transport protocols for soft real-time applications.

A novel QoS modeling approach for soft real-time systems with performance guarantees

2009

This paper introduces a systematic approach for modeling QoS requirements of soft real-time systems with stochastic responsiveness guarantees. While deadline miss ratio and its proposed extensions have been considered for evaluating firm real-time systems, this work brings out its limitations for assessing the performance of emerging computer services operating over communication infrastructures with non-deterministic dynamics. This work explains how delay frequencies and delay lengths can be both represented into a single quantitative meaningful measure for performance evaluation of soft real-time constrained computer applications. It also explores the presented approach in the design of scheduling strategies which can ground novel business models for QoS-enabled service-oriented systems.

A connection-oriented network architecture with guaranteed QoS for future real-time applications over the Internet

Computer Networks, 2006

The QoS provided by todayÕs best effort Internet is not good enough, especially for real-time interactive traffic categorized as Premium Traffic (PT). It is believed that QoS guarantees could be better provided by connection-oriented networks such as IP/MPLS. However, these connection-oriented networks are inherently more prone to network failures. Failures of connection-oriented MPLS can be broadly classified into two types namely: link/path failures and degraded failures. Degraded failures that account for about 50% of total failures are detected by the timers maintained at the control plane peers. The control plane and the data plane of IP/MPLS packet networks are logically separated and therefore a failure in the control plane should not immediately disconnect the communications in the data plane. The Virtual Path Hopping (VPH) concept in this study distinguishes these two types of failures and avoids the disconnections of communications in the data plane due to degraded failures. Thereby it reduces the number of failures in the data plane. Computer simulations were performed and the results indicate that VPH is a proactive technique that minimizes failures in the data plane. The proposed Dynamic Virtual Path Allocation (DVPA) algorithm improves the availability of the connection-oriented networks by overcoming link/path failures, especially for PT, without compromising the network resource utilization efficiency. Comprehensive simulations were performed to evaluate the DVPA algorithm and the results show the improvements that DVPA can achieve. Therefore implementation of the DVPA algorithm in conjunction with VPH would improve the reliability and availability aspects of QoS in connection-oriented IP/MPLS packet networks.

QoS Support for Real-Time Flows in Internet Routers

This paper addresses how to offer a specific QoS for soft-real time distributed applications over the Internet. The approach here proposed is entrusting the routers with the task of providing diversified scheduling for real-time and non-real-time flows, keeping the two types of traffic into separate queues and applying a deadline-based scheduling to real-time flows and a FIFO policy to non-real-time traffic. The scheduling techniques proposed for real-time flows are an adaptation of the Earliest Deadline First algorithm. The performances of the approach have been measured on a real test bed and are discussed in the paper.

Quality of Service Scheduling in Real-Time Systems

2008

In this paper, we deal with dynamic scheduling components integrating new Quality of Service (QoS) functionalities into a Linux-based real-time operating system. In our approach, periodic tasks allow occasional deadline violations within given bounds specified according to the Skip-Over task model. Hence, every task has a minimal QoS guarantee which is expressed by the ratio of periodic task instances which must complete before their deadline. The work stated here provides two on-line scheduling algorithms, namely RLP and RLP/T, which enhance the existing Skip-Over algorithms. More specifically, the proposed algorithms aim at improving the actual QoS observed for periodic tasks (which is always greater or equal to the QoS guarantee). These novel scheduling techniques rely on the EDL (Earliest Deadline as Late as possible) scheduling strategy. Simulation results show the performance of RLP and RLP/T with respect to basic Skip-Over algorithms. Finally, we present the integration of these QoS scheduling services into CLEOPATRE open-source component library, a patch to Linux/RTAI.

Scheduling for Cloud-Based Computing Systems to Support Soft Real-Time Applications

ACM Transactions on Modeling and Performance Evaluation of Computing Systems, 2017

Cloud-based computing infrastructure provides an efficient means to support real-time processing workloads, for example, virtualized base station processing, and collaborative video conferencing. This article addresses resource allocation for a computing system with multiple resources supporting heterogeneous soft real-time applications subject to Quality of Service (QoS) constraints on failures to meet processing deadlines. We develop a general outer bound on the feasible QoS region for non-clairvoyant resource allocation policies and an inner bound for a natural class of policies based on dynamically prioritizing applications’ tasks by favoring those with the largest (QoS) deficits. This provides an avenue to study the efficiency of two natural resource allocation policies: (1) priority-based greedy task scheduling for applications with variable workloads and (2) priority-based task selection and optimal scheduling for applications with deterministic workloads. The near-optimality...

NetQoPE: A Model-Driven Network QoS Provisioning Engine for Distributed Real-time and Embedded Systems

2008 IEEE Real-Time and Embedded Technology and Applications Symposium, 2008

This paper provides two contributions to the study of quality of service (QoS)-enabled middleware that supports the network QoS requirements of distributed real-time and embedded (DRE) systems. First, we describe the design and implementation of NetQoPE, which is a model-driven component middleware framework that shields applications from the details of network QoS mechanisms by (1) specifying per-flow network QoS requirements, (2) performing resource allocation and validation decisions (such as admission control), and (3) enforcing per-flow network QoS at runtime. Second, we evaluate the effort required and flexibility of using NetQoPE to provide network QoS assurance to end-to-end application flows. Our results demonstrate that NetQoPE can provide network-level differentiated performance to each application flow without modifying its programming model or source code, thereby providing greater flexibility in leveraging network-layer mechanisms.

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IP Quality of Service Support for Soft Real-Time Applications

To obtain acceptable timeliness performance for emerging large-scale distributed real-time control applications operating in large IP internetworks, a scalable quality of service (QoS) architecture is needed. In this paper, we propose a scalable QoS architecture (abbreviated as RTQoS) in support of real-time systems, one that implements real-time scheduling at end-hosts and stateless QoS in the core routers. We address challenges and explore potential benefits achieved by integrating network services with real-time systems, through the use of a network testbed. Experimental evaluation demonstrates the RTQoS architecture as a promising approach for soft real-time applications that are subject to time/utility function time constraints and utility accrual optimality criteria.

Quality of service control in soft real-time applications

2003

In this paper we present results obtained in the context of Quality of Service (QoS) control for soft real-time applications. The discussion addresses the issue of dynamically adjusting the bandwidth for a set of periodic tasks, when a reservation-based (RB) CPU scheduling policy is used. RB techniques are particularly suitable for this kind of applications since they allow an accurate mathematical modelling of the dynamic evolution of the QoS experienced by tasks. Based on this model, a control policy guaranteeing specified QoS levels for different tasks is illustrated, along with necessary and sufficient conditions for its existence. Moreover, the problem of steering a task QoS back into its nominal level is tackled, in response to deviations due to temporary overload conditions. Simulation results are reported, for the purpose of validating the approach.

Evolution of the Internet QoS and support for soft real-time applications

Proceedings of the IEEE, 2003

The past few years have witnessed the emergence of many real-time networked applications on the Internet. These types of applications require special support from the underlying network such as reliability, timeliness, and guaranteed delivery, as well as different levels of ...

A service oriented monitoring framework for soft real-time applications

2010

The advancements in distributed computing have driven the emergence of Service Oriented infrastructures that allow for on-demand provision of ICT assets. Taking into consideration the complexity of distributed environments, significant challenges exist in providing and managing the offered on-demand resources with the required level of Quality of Service (QoS), especially for real-time interactive multimedia applications. Monitoring mechanisms are a fundamental part in service-based platforms that support realtime QoS guarantees by providing coherent and consistent real-time attributes at various levels of the infrastructure (application, network, storage, processing). In this paper we present an architectural design and implementation of a complete monitoring framework for measuring QoS at both application and infrastructure levels targeting trigger events for runtime adaptability of resource provisioning estimation and decision-making. We also demonstrate the operation of the implemented mechanism and evaluate its effectiveness using an application scenario, namely Film Postproduction.

On the Integration of Application Level and Resource Level QoS Control for Real-Time Applications

IEEE Transactions on Industrial Informatics, 2000

We consider a dynamic set of soft real-time applications using a set of shared resources. Each application can execute in different modes, each one associated with a level of Quality of Service (QoS). Resources, in their turn, have different modes, each one with a speed and a power consumption, and are managed by a Reservation Based scheduler enabling a dynamic allocation of the fraction of resources (bandwidth) assigned to each application.

Supporting application network flows with multiple QoS constraints

2009

There is a growing need to support real-time applications over the Internet. Real-time interactive applications often have multiple quality-of-service (QoS) requirements which are application specific. Provisioning QoS in the Internet through IP routing-Intserv or Diffserv-faces many technical challenges, and is also deterred by the huge deployment issues. As an alternative, application providers often build their own applicationspecific overlay networks to meet their QoS requirements. In this paper, we present a unified framework which can serve diverse applications with multiple QoS constraints. Our scalable flow route management architecture, called MCQoS, employs a hybrid approach using a path vector protocol to disseminate aggregated path information combined with ondemand path discovery to find paths that match the diverse QoS requirements. It uses a distributed algorithm to dynamically adapt to an alternate path when the current path fails to satisfy the required QoS constraints. We do large-scale simulation and theoretical analysis to show that our approach is both efficient and scalable, and that it substantially outperforms the state of the art protocols in accuracy. Our simulation results show that MCQoS can reduce the false negative percentage to less than 1% compared with 5-10% in other approaches, and eliminates false positives, whereas other schemes have false positive rates of 10-20% with minimal increase in protocol overhead. Finally, we implemented and deployed our system on the Planetlab testbed for evaluation in a real network environment.

Scalable QoS Guaranteed Communication Services for Real-Time Applications

2000

In this paper, we propose an approach to flow-unaware admission control, which is combination with an aggregate packet forwarding scheme, improves scalability of networks while guaranteeing end-to-end deadlines for realtime applications. We achieve this by using an off-line delay computation and verification step, which allows to reduce the overhead at admission control while keeping admission probability and resources utilization high. Our evaluation data show our system's admission probabilities are very close to those of significantly more expensive flow-aware approaches. At the same time, admission control overhead during flow establishment is very low. Our results therefore support the claim from the DS architecture literature that scalability can be achieved through flow aggregation without sacrificing resource utilization and with significant reduction in run time overhead. ¡ . Each edge router is supposed to aggregate the individual flows into a small number of such aggregate flows. In this fashion, the DS model makes the ¢ In the following, we will use the term flow to indicate a stream of data between a source and a destination, and the term connection to indicate the virtual circuit that needs to be established to carry the flow.

Adaptive Failover for Real-Time Middleware with Passive Replication

2009

Supporting uninterrupted services for distributed soft real-time applications is hard in resource-constrained and dynamic environments, where processor or process failures and system workload changes are common. Fault-tolerant middleware for these applications must achieve high service availability and satisfactory response times for client applications. Although passive replication is a promising fault tolerance strategy for resource-constrained systems, conventional client failover approaches are non-adaptive and load-agnostic, which can cause system overloads and significantly increase response times after failure recovery. This paper presents four contributions to the study of passive replication for distributed soft real-time applications. First, it describes how our Fault-tolerant Loadaware and Adaptive middlewaRe (FLARe) dynamically adjusts failover targets at runtime in response to system load fluctuations and resource availability. Second, it describes how FLARe's overload management strategy proactively enforces desired CPU utilization bounds by redirecting clients from overloaded processors. Third, it presents the design and implementation of FLARe's lightweight middleware architecture that manages failures and overloads transparently to clients. Finally, it presents experimental results on a distributed Linux testbed that demonstrate how FLARe adaptively maintains soft real-time performance for clients operating in the presence of failures and overloads with negligible runtime overhead.

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Issues in Managing Soft QoS Requirements in Distributed Systems Using a Policy-Based Framework

Policies for Distributed Systems and Networks, 2001

We address the problem of Quality of Service (QoS) require- ments for multimedia applications (e.g., distance education, telemedicine, electronic commerce). These applications need to be able to co-exist with more traditional applications for transaction and data processing and have soft real-time requirements. Unlike most other work in QoS man- agement, we provide a framework that does not require users or

Online Real-Time Preemptive Scheduling of Jobs with Deadlines

Lecture Notes in Computer Science, 2000

In this paper, we derive bounds on performance guarantees of online algorithms for real-time preemptive scheduling of jobs with deadlines on K machines when jobs are characterized in terms of their minimum stretch factor α (or, equivalently, their maximum execution rate r = 1/α). We consider two well known preemptive models that are of interest from practical applications: the hard real-time scheduling model in which a job must be completed if it was admitted for execution by the online scheduler, and the firm real-time scheduling model in which the scheduler is allowed not to complete a job even if it was admitted for execution by the online scheduler. In both models, the objective is to maximize the sum of execution times of the jobs that were executed to completion, preemption is allowed, and the online scheduler must immediately decide, whenever a job arrives, whether to admit it for execution or reject it. We measure the competitive ratio of any online algorithm as the ratio of the value of the objective function obtained by this algorithm to that of the best possible offline algorithm. We show that no online algorithm can have a competitive ratio greater than 1 − (1/α) + ε for hard real-time scheduling with K ≥ 1 machines and greater than 1 − (3/(4 α)) + ε for firm real-time scheduling on a single machine, where ε > 0 may be arbitrarily small, even if the algorithm is allowed to know the value of α in advance. On the other hand, we exhibit a simple online scheduler that achieves a competitive ratio of at least 1 − (1/α) in either of these models with K machines. The performance guarantee of our simple scheduler shows that it is in fact an optimal scheduler for hard real-time scheduling with K machines. We also describe an alternative scheduler for firm real-time scheduling on a single machine in which the competitive ratio does not go to zero as α approaches 1. Both of our schedulers do not know the value of α in advance.