We investigate the use of priority mechanisms when assigning service engineers to customers as a tool for service differentiation. To this end, we analyze a non-preemptive M/G/c priority queue with various customer classes. For this queue, we present various accurate and fast methods to estimate the first two moments of the waiting time per class given that all servers are occupied. These waiti...

The increasing significance of operating systems (OSs) in the development internet things (IoT) has emerged last decade. An event-driven OS is memory efficient and suitable for resource-constrained IoT devices wireless sensors, although program’s control flow, which determined by events, not always obvious. A multithreaded with sequential flow often considered clearer. However, this approach me...

Handling cache related preemption delay (CRPD) in a preemptive scheduling context for real-time systems stays an open subject despite of its practical importance. Priority assignment algorithms and feasibility tests are usually based on the assumption that preemption cost is negligible. Then, a system that could be schedulable at design time can fail to meet its timing constraints in practice d...

In this paper, we use matrix–analytic methods to construct a novel queueing model called the dual queue. The dual queue has the additional feature of a priority scheme to assist in congestion control. Detailed structure of the infinitesimal generator matrix is derived and used in the solution process. Using a computational algorithm, which utilises a combination of iterative and elementary matr...

In this paper, we study the problem of the fixed priority preemptive scheduling of hard real-time tasks. We consider independent tasks, which are characterized by a period, a hard deadline, a computation time, and an offset (the time at which the first request is issued) where the latter can be chosen by the scheduling algorithm. Considering only the synchronous case is very pessimistic for off...

Cache memory is used in almost all computer systems today to bridge the ever increasing speed gap between the processor and main memory. However, its use in multitasking computer systems introduces additional preemption delay due to reloading of memory blocks that were replaced during preemption. This cache-related preemption delay poses a serious problem in real-time computing systems where pr...

We study MX/G/1 nonpreemptive and preemptive-resume priority queues with/without vacations under random order of service (ROS) discipline within each class. By considering the conditional waiting times given the states of the system, which an arbitrary message observes upon arrival, we derive the Laplace-Stieltjes transforms of the waiting time distributions and explicitly obtain the first two ...

In this paper we present a global scheduling method for shared memory multiprocessor systems that provides a fixed-priority preemptive scheduling of periodic tasks, hard aperiodic tasks and soft aperiodic tasks on a set of identical processors. The method is based on the functioning of the Dual Priority Scheduling Algorithm extended to work in a multiprocessor environment. This algorithm guaran...

The present paper deals with the problem of calculating queue length distributions in a priority queueing model with a preemptive-resume policy under the assumption of general arrival and service distributions. The multi-queue priority system is decomposed into single-queue vacation systems, for which the visit and inter-visit distributions are approximated by the idle and busy period of a ΣGI/...

In this paper we present the approximate waiting time analysis of two class non-preemptive priority queues. The traffics of the queue are characterized by ”two parameter description”, which means that the mean and the squared coefficient of variation of the inter arrival times and of the service times are given. The solution is based on the separate analysis of the low and high priority queue. ...