This paper presents a heavy-traffic analysis of the behavior of a single-server queue under an Earliest-Deadline-First (EDF) scheduling policy, in which customers have deadlines and are served only until their deadlines elapse. The performance of the system is measured by the fraction of reneged work (the residual work lost due to elapsed deadlines), which is shown to be minimized by the EDF po...

The most frequency used goodness of fit tests are based on measuring the distance between the theoretical distribution function and the empirical distribution function (EDF), but presence of outliers influences these tests strongly. In this study, we propose a simple robust method for goodness of fit test by using the “Forward Search” (FS) method. The FS method is a powerful general method for ...

This paper introduces an analytical method for approximating the performance of a two-class priority M/M/1 system. The system is fully non-preemptive. More specifically, the prioritized class-1 jobs are real-time and served with the non-preemptive earliest-deadline-first (EDF) policy, but despite their priority cannot preempt any non real-time class-2 job. The waiting class-2 jobs can only be s...

Real-time communication is important for time-critical multimedia applications. However, conventional real-time schedulers such as EDF (Earliest Deadline First) and RM (Rate Monotonic) are designed for task sets with sophisticated characteristics. They can perform well in the idea network with precise workloads. But, in a realistic network with shared bandwidth and unpredictable workloads, thei...

We present a real-time, Linux-based testbed called LITMUS, which we have developed for empirically evaluating multiprocessor real-time scheduling algorithms. We also present the results from such an evaluation, in which partitioned earliest-deadline-first (EDF) scheduling, preemptive and nonpreemptive global EDF scheduling, and two variants of the global PD Pfair algorithm were considered. The ...

Various techniques have been proposed to achieve good QoS for diverse application types at network nodes. In order to supply the various QoS requirements for different kinds of applications, new scheduling policies need to be developed and evaluated. Many scheduling techniques have been proposed to respond to the temporal requirements of real-time flows. We propose a new scheduling Hierarchical...

In this paper, we consider a set of real-time periodic tasks where some tasks are preferably executed as soon as possible (ASAP) and others as late as possible (ALAP) while still meeting their deadlines. After introducing the idea of preference-oriented (PO) execution, we formally define the concept of PO-optimality. For fully-loaded systems (with 100% utilization), we first propose a PO-optima...

Quality of Service (QoS) in terms of end-to-end delay guarantees to real-time applications is an important issue in emerging broadband packet networks. Earliest Deadline First (EDF) scheduling, in conjunction with per-hop traffic shaping (jointly called Rate Controlled EDF or RC-EDF) has been recognised as an effective means of end-to-end deterministic delay provisioning. This paper addresses t...

We address the issue of reserving resources at packet switches along the path of connections requiring a deterministic end-to-end delay bound. The switches are assumed to schedule outgoing packets using either the Packet-by-Packet Generalized Processor Sharing (PGPS) or the Rate-Controlled Earliest-Deadline First (RC-EDF) scheduling disciplines. We propose a set of resource reservation policies...

The purpose of this paper is to present the density of a task as a heuristic to schedule real-time tasks. The density of a task is defined as the ratio between the computation time of the task and the minimum of its relative deadline and period. We propose the Highest Task Density First (HTDF) algorithm to schedule tasks in real-time systems. HTDF is a dynamic priority scheduling algorithm that...