In this paper we present improved techniques for the schedulability analysis of tasks with precedence relations in multiprocessor and distributed systems, scheduled under a preemptive fixed priority scheduler. Recently developed techniques, based on the analysis of tasks with dynamic offsets, take into account the precedence relations between tasks only indirectly, through terms iteratively est...

We present new results in fixed priority scheduling for imprecise computation in real-time systems. Imprecise computation has not been popularized enough for reasons which are rooted from the task model, scheduling methods (EDF-based) and general system support. Audsley et al. have devised schedulability tests for guaranteeing mandatory computation while incorporating unbounded optional compone...

In this work, we revisit the theory underlying a range of time-dependent priority disciplines, and extend it to include the requirements of a class of applications that has not been studied in the past. Specifically, we target applications and services in which a scarce resource, or a fraction thereof, has to be awarded to a large number of concurrent requests. We thus consider an heavy traffic...

0 50 100 Interarrival Delay Jitter Offered Load Percentage Figure 15: A three-dimensional plot of the Delay Jitter histogram at the destination for four VBR connections for diierent background non-QoS (datagram) loads with preemptive priority to QoS Virtual Channels. Note the log scale for the delay jitter in byte times at the destination. we have presented and evaluated several diierent approa...

In this paper, we consider two single server queueing systems to which customers of distinct priorities (P1 and P2) arrive according a Marked Markovian arrival process (MMAP). They are served phase type distributions. The probability P1 customer feedback is θ on completion his service. (P1) customers, as well P2 join the low priority queue. Low (P2) taken for service from head line whenever que...

We give a closed-form expression for the long-run average cost and the bias vector in a twoclass exponential preemptive resume priority queue with holding and switching costs. The bias vector is the sum of a quadratic function of the number of customers in each priority class and an exponential function of the number of customers in the high priority class. We use this result to perform a singl...

We derive the performance measures for non-priority customers in a priority single-server queue with two types of Markovian arrival processes (MAPs). One type of customers has preemptive resume (or repeat) priority over the other. We regard the model with two types of MAP arrivals as an MAP/SM/l queue with only non-priority customers arrivals, semi-Markovian service times and some server vacati...

Scheduling theories for fixed priority scheduling are now sufficiently mature that a genuine engineering approach to the construction of hard real-time systems is possible. In this paper we review recent advances. A flexible computational model is adopted that can accommodate periodic and sporadic activities, different levels of criticality, process interaction and blocking, cooperative schedul...

Abstract: Generally in call centers, voice calls (say Type 1 calls) are given higher priority over e-mails (say Type 2 calls). An arriving Type 1 call has a preemptive priority over a Type 2 call in service, if any, and the preempted Type 2 call enters into a retrial buffer (of finite capacity). Any arriving call not able to get into service immediately will enter into the pool of repeated call...

In this paper, a multi-server queueing system providing service to two correlated flows of requests was considered. Non-preemptive priority granted one flow via the preliminary delay in intermediate buffers with different rates extracting from buffers. Customers’ impatience during waiting and main taken into account. The possibility use results mathematical analysis for managerial goals is nume...