Multiprogrammed Computer System Research Articles

Improvised Optimum Multilevel Dynamic Round Robin Algorithm for Optimizing CPU Scheduling

scheduling has strong effect on resource utilization as well as overall performance of the system. In order to simulate the behavior of multiple jobs in a multiprogramming computer system needs to be specified. The most important aspect of job scheduling is the ability to create a multi-tasking environment. The intention should be allowed as many as possible running processes at all time in order to make best use of CPU. Round Robin algorithm performs optimally in timeshared systems, but it is not suitable for soft real time systems, because it gives more number of context switches, larger waiting time and larger response time. The main objective of this paper is to improve the previous OMDRRS with calculates intelligent time slice and warps after every round of execution and assumed that all the processes were come at randomly as well as all the processes have priority. In order to simulate the behavior of various CPU scheduling algorithms and to improve Round Robin scheduling algorithm using dynamic time slice concept, we purpose new improved CPU scheduling algorithm called Optimum Dynamic Round Robin Scheduling (OMDRR). Our experimental results show that our proposed algorithm performs better in terms of reducing the number of context switch, average waiting time and average turnaround time.

Behaviour of passage time for a queueing network model withfeedback: a simulation study

The study of the queueing system presented in this note was motivated by its possible application to a multiprogramming computer system. The paper considers a closed network with two service centres with feedback. The steady‐state behaviour of the passage time, the random times for a job to traverse a portion of the network, is examined through simulation. The model can be applied to a twin‐processor multiprogramming computer system.

Analytical Modelling of a Refined Fcfs Queueing Discipline in Multiprogrammed Parallel Processing Systems

A multiprogrammed (or partitionable) parallel computer system can be partitioned into subsystems which are allocated to independent jobs. The performance of such a parallel processing system is deter-mined by the system partitioning strategy and the job scheduling policy adopted. In this paper, we consider the impact of a job scheduling algorithm on the system performance, mainly the average job response time. A refined First-Come-First-Serve (FCFS) queueing discipline called FCFS/SJE is studied, which, when there are not enough processors available for large jobs in the front of a waiting queue, schedules small jobs behind these large jobs earlier. We develop a multi-server queueing system for modelling multiprogrammed parallel processing systems. A system is specified by the number of processors and jobs are characterized by a probability distribution of the number of processors requested, a Poisson arrival process, and an exponential distribution of execution time. Our analysis as well as simulation indicate that FCFS/SJE results in a noticeable improvement on system performance compared with FCFS.

Random Resource Allocation Graphs and the Probability of Deadlock

Resource allocation graphs are directed bipartite graphs satisfying certain constraints. The two partitions of the vertex set correspond to the processes and resources of a multi-programming computer system, and the edges indicate resource allocations and requests. When all the resources are distinguishable, existence of a cycle in such a graph is equivalent to deadlock in the system. The main results here are exact and asymptotic formulas for the number of resource allocation graphs and acyclic resource allocation graphs with m processes, n allocated resources, and q edges. If a uniform probability distribution is taken on such graphs, then the proportion of blocked processes, $( q - n )/m$, determines the asymptotic behavior of the probability of deadlock: If $( q - n )/m \to 0$, then the probability of deadlock is asymptotic to 0, and if $( q - n )/m \to \alpha > 0$, then the probability is asymptotic to a positive value. Similar formulas are also given in terms of m and n only.

Realtime multiprogramming system for mine control centre

The paper discusses some issues in the development of a modular realtime program for an industrial microcomputer system. Experience gained in the design of a multiprogramming computer system for the Brown Coal Mine Control Centre in Betchatow (Poland) is presented. Brief remarks about the aims of the system are followed by an analysis of the choice of programming tools and methods, as well as their influence on the efficiency of the program creation process and its reliability. The hierarchical internal structure of the program is also presented.

Two-Stage Cyclic Queues with Nonexponential Servers: Steady-State and Cyclic Time

We consider a closed two-stage cyclic queueing model for a multiprogrammed computer system. Assuming one general server and one server whose service time distribution is a mixture of Erlang distributions, we compute both the steady-state distribution at departure points and the Laplace-Stieltjes transform of the cycle time, given the state of system at the beginning of the cycle. We also find delay time and cycle time distributions for systems both in and out of equilibrium.

Cycle Times in Two-Stage Closed Queueing Networks: Applications to Multiprogrammed Computer Systems with Virtual Memory

We compute the distribution of the time for a sequence of successive cycles in a two-stage exponential queue which represents a multiprogrammed computer system.

Sojourn Time Distribution in a Multiprogrammed Computer System

We present a method for calculating the moments and the distribution of sojourn time in a multiprogrammed computer system. We assume that the CPU and I/O subsystem can be represented by a general state-dependent server who works according to the processor sharing discipline. Further, at most m jobs may be simultaneously receiving service. Thus, m is the multiprogramming level of the system. The arrival of jobs occurs according to a Poisson process, and the arrivals must wait in a waiting area if m jobs are already receiving service. The method presented may be useful in designing the multiprogramming level needed to meet certain objectives on the characteristics of the sojourn time.

Aggregation with an error of O (ε 2 )

An aggregative technique to obtain an improved approximation of the equilibrium vector of a Markov chain with a nearly completely decomposable transition matrix is presented. The technique is demonstrated on a model of a multiprogrammed computer system.

Optimality of scheduling policy for processing a job stream

It has been claimed on the basis of empirical studies that a CPU scheduling policy, whereby I/Obound jobs are given preemptive priority over CPU-bound jobs, produces the highest overall CPU utilization of multiprogrammed computer systems. However, a theoretical result has shown that the CPU utilization is independent of CPU scheduling in a finite-source queuing model of multiprogrammed systems. This paper aims at resolving this seeming conflict and gaining some insight into CPU scheduling by analyzing a Markovian model of job-stream processing. The model studied consists of an infinite backlog of jobs of two classes (a job stream} and a multiple-resource system (the model of a multiprogrammed system which processes the job stream}; the system consists of a cyclic queue of two nodes--a single (CPU) server and an infinite (I/O) server. The system contains a fixed number of jobs concurrently; the values of parameters describing each job class are distinct except for the mean I/O service time. The following result is obtained under the near-complete decomposability of the model: The maximum overall CPU server utilization (and the maximum throughput) is achieved by scheduling policy whereby jobs of the class having a shorter mean CPU service time are given preemptive priority over others at the CPU server, although the CPU server utilization is independent of CPU scheduling so long as the set of jobs in the system remains fixed.

Equivalent Queueing Networks and Their Use in Approximate Equilibrium Analysis

Most Markovian queueing networks that arise as models of stochastic congestion systems (e.g., communication networks and multiprogrammed computer systems) do not have a product form in their stationary probability distributions, and hence are not amenable to the simplicity of product-form analysis. In this paper we suggest an approach for systematically examining the validity of a class of approximation schemes that is based on the idea of equivalent networks and is used for the approximate equilibrium analysis of nonproduct-form networks. We study equivalent networks, and prove a generalization of the so-called “Norton's” Theorem for closed product-form networks in order to study and generalize the equivalent flow method for the approximate analysis of nonproduct-form queueing networks. We then present the results of a study of the approximation scheme as applied to a type of network model (called a central-server model) that arises frequently in modeling multiprogrammed computer systems. In this model the central server uses a priority discipline, so the resulting network is nonproduct form. This study demonstrates the situations under which the approximation can be expected to do well or poorly and the kinds of errors it introduces.

Programming semantics for multiprogrammed computations

The semantics are defined for a number of meta-instructions which perform operations essential to the writing of programs in multiprogrammed computer systems. These meta-instructions relate to parallel processing, protection of separate computations, program debugging, and the sharing among users of memory segments and other computing objects, the names of which are hierarchically structured. The language sophistication contemplated is midway between an assembly language and an advanced algebraic language.

A note on the cpu usage of a computer system with many I/O channels

A recursive formula, to model CPU performance of a multiprogrammed computer system, is derived using a conventional mathematical model. This new formula computes faster and gives reliable results in cases where the conventional one fails to produce any.

Optimal control of Markovian queueing systems

AbstractDynamic optimization of queueing systems is treated by optimal control theory. This work is based on modelling the queueing problem as a time‐varying continuous Markov chain. Necessary and sufficient conditions are given for a broad class of problems which include both scalar and Markovian dynamic programming control structures. Continuity of the switching function is used to characterize optimality near the end points of the horizon. Special properties of the model are exploited to ensure the absence of singular subarcs. Numerical results based on the use of a gradient algorithm report the effect of increasing the system capacity, a comparison of scalar versus Markovian dynamic programming controls, and an application to a multiprogrammed computer system.

Optimization of Memory Hierarchies in Multiprogrammed Computer Systems With Fixed Cost Constraint

This paper presents, using queuing theory and optimization techniques, an approach for estimating the optimal capacities and speeds of the memory levels in a memory hierarchy operating in the multiprogrammed environment. Optimality is defined with respect to mean system response time under a fixed cost constraint. It is assumed that the number of levels in the hierarchy as well as the capacity of the lowest level are known. The effect of the storage management strategy is characterized by the miss ratio function which, together with the device technology cost functions, is assumed to be representable by power functions. It is shown that as the arrival rate of processes and/or the number of active processes in the system increase, the optimal solution deviates considerably from that under a uniprogrammed environment. It is also shown that the solution obtained is the global optimum.

Incorporating System Overhead in Queuing Network Models

Multiclass queuing network models of multiprogramming computer systems are frequently used to predict the performance of computing systems as a function of user workload and hardware configuration. This paper examines three different methods for incorporating operating system overhead in multiclass queuing network models. The goal of the resultant model is to provide an accurate account of the processing performance and the system CPU overhead of each of the several different types of jobs (batch, timesharing, transaction processing, etc.) that together make up the multiprogramming workload. The first method introduces an operating sysbtm workload consisting of a fixed number of jobs to represent system CPU overhead processing. The second method extends the jobs' CPU service requests to include explicitly the CPU overhead necessary for system processing. The third method employs a communicating set of user and system job classes so that the CPU overhead can be modeled by switching jobs from user to system class whenever they require system CPU service. The capabilities and accuracy of the three methods are assessed and compared against performance and overhead data measured on a Univac 1110 computer.

Optimal control of finite source priority queues with computer system applications

The paper deals with the derivation of optimal control rules for finite source queueing systems with preemptive resume service discipline. The three performance measures considered are: server utilization, mean queue length and throughput. It is indicated how the results on optimal control can be applied to multiprogrammed computer systems and some numerical examples are given.

Simulation of Response Times in Finite-Capacity Open Networks of Queues

We extend to two types of finite-capacity open networks a previously developed technique for the estimation by simulation of job response time characteristics in closed queuing network models of multiprogrammed computer systems. Particular stochastic point processes associated with a Markov renewal process generate arrivals to the networks. Such arrival patterns are useful for representation of the work load of the computer system being modeled. The regenerative method for simulation of stochastic systems and the idea of tracking a marked job in the network form the basis for the estimation technique. We also report illustrative simulation results.

An Analytic Model of the VM/370 System

This paper describes an analytic model of an interactive multiprogrammed computer system. The model accepts a multiple-user-class, transaction-oriented workload description and a system configuration description, and it produces predictions of resource utilizations, transaction rates, and average transaction response times. The solution method involves nearly complete decomposition, with a closed queuing network representing the multiprogrammed set. Asymptotic formulas are used to generate good initial guesses for an overall iterative scheme. Extensive validation results are presented.

Multivariate point process models for response times in multiprogrammed systems

We consider the formulation of marked multivariate point process models for job response times in multiprogrammed computer systems. Complementing queueing network representation of the structure of the system to be modeled, the particularR-process (Response time process) model we propose permits representation of resource contention, facilitates the incorporation of realistic workload characteristics into system performance predictions, and can reproduce inhomogeneities observed in running systems. Specification of the structure of theR-process model is conditional on workload marks; this effectively separates the difficult problem of formal representation of workload characteristics from the overall problem of response time prediction. To illustrate these ideas, an application to database management systems is considered. Evidence of the predictive capability of theR-process model, based on statistical analysis of response time data from an IMS system, is also given.