Demand-based coscheduling of parallel jobs on multiprogrammed multiprocessors

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 92-94).by Patrick Gregory Sobalvarro.Ph.D

Scalable Resource Management in High Performance Computers £

Abstract Clusters of workstations have emerged as an importan

A Decision-Process Analysis of Implicit Coscheduling

This paper presents a theoretical framework based on Bayesian decision theory for analyzing recently reported results on implicit coscheduling of parallel applications on clusters of workstations. Using probabilistic modeling, we show that the approach presented can be applied for processes with arbitrary communication mixes. We also note that our approach can be used for deciding the additional spin times in the case of spin-yield.Finally, we present arguments for the use of a different notion of fairness than assumed by prior work.International Conference on Parallel and Distributed Computing</i

"Virtual malleability" applied to MPI jobs to improve their execution in a multiprogrammed environment"

This work focuses on scheduling of MPI jobs when executing in shared-memory multiprocessors (SMPs). The objective was to obtain the best performance in response time in multiprogrammed multiprocessors systems using batch systems, assuming all the jobs have the same priority. To achieve that purpose, the benefits of supporting malleability on MPI jobs to reduce fragmentation and consequently improve the performance of the system were studied. The contributions made in this work can be summarized as follows:· Virtual malleability: A mechanism where a job is assigned a dynamic processor partition, where the number of processes is greater than the number of processors. The partition size is modified at runtime, according to external requirements such as the load of the system, by varying the multiprogramming level, making the job contend for resources with itself. In addition to this, a mechanism which decides at runtime if applying local or global process queues to an application depending on the load balancing between processes of it. · A job scheduling policy, that takes decisions such as how many processes to start with and the maximum multiprogramming degree based on the type and number of applications running and queued. Moreover, as soon as a job finishes execution and where there are queued jobs, this algorithm analyzes whether it is better to start execution of another job immediately or just wait until there are more resources available. · A new alternative to backfilling strategies for the problema of window execution time expiring. Virtual malleability is applied to the backfilled job, reducing its partition size but without aborting or suspending it as in traditional backfilling. The evaluation of this thesis has been done using a practical approach. All the proposals were implemented, modifying the three scheduling levels: queuing system, processor scheduler and runtime library. The impact of the contributions were studied under several types of workloads, varying machine utilization, communication and, balance degree of the applications, multiprogramming level, and job size. Results showed that it is possible to offer malleability over MPI jobs. An application obtained better performance when contending for the resources with itself than with other applications, especially in workloads with high machine utilization. Load imbalance was taken into account obtaining better performance if applying the right queue type to each application independently.The job scheduling policy proposed exploited virtual malleability by choosing at the beginning of execution some parameters like the number of processes and maximum multiprogramming level. It performed well under bursty workloads with low to medium machine utilizations. However as the load increases, virtual malleability was not enough. That is because, when the machine is heavily loaded, the jobs, once shrunk are not able to expand, so they must be executed all the time with a partition smaller than the job size, thus degrading performance. Thus, at this point the job scheduling policy concentrated just in moldability.Fragmentation was alleviated also by applying backfilling techniques to the job scheduling algorithm. Virtual malleability showed to be an interesting improvement in the window expiring problem. Backfilled jobs even on a smaller partition, can continue execution reducing memory swapping generated by aborts/suspensions In this way the queueing system is prevented from reinserting the backfilled job in the queue and re-executing it in the future.Postprint (published version

"Virtual malleability" applied to MPI jobs to improve their execution in a multiprogrammed environment"

This work focuses on scheduling of MPI jobs when executing in shared-memory multiprocessors (SMPs). The objective was to obtain the best performance in response time in multiprogrammed multiprocessors systems using batch systems, assuming all the jobs have the same priority. To achieve that purpose, the benefits of supporting malleability on MPI jobs to reduce fragmentation and consequently improve the performance of the system were studied. The contributions made in this work can be summarized as follows:· Virtual malleability: A mechanism where a job is assigned a dynamic processor partition, where the number of processes is greater than the number of processors. The partition size is modified at runtime, according to external requirements such as the load of the system, by varying the multiprogramming level, making the job contend for resources with itself. In addition to this, a mechanism which decides at runtime if applying local or global process queues to an application depending on the load balancing between processes of it. · A job scheduling policy, that takes decisions such as how many processes to start with and the maximum multiprogramming degree based on the type and number of applications running and queued. Moreover, as soon as a job finishes execution and where there are queued jobs, this algorithm analyzes whether it is better to start execution of another job immediately or just wait until there are more resources available. · A new alternative to backfilling strategies for the problema of window execution time expiring. Virtual malleability is applied to the backfilled job, reducing its partition size but without aborting or suspending it as in traditional backfilling. The evaluation of this thesis has been done using a practical approach. All the proposals were implemented, modifying the three scheduling levels: queuing system, processor scheduler and runtime library. The impact of the contributions were studied under several types of workloads, varying machine utilization, communication and, balance degree of the applications, multiprogramming level, and job size. Results showed that it is possible to offer malleability over MPI jobs. An application obtained better performance when contending for the resources with itself than with other applications, especially in workloads with high machine utilization. Load imbalance was taken into account obtaining better performance if applying the right queue type to each application independently.The job scheduling policy proposed exploited virtual malleability by choosing at the beginning of execution some parameters like the number of processes and maximum multiprogramming level. It performed well under bursty workloads with low to medium machine utilizations. However as the load increases, virtual malleability was not enough. That is because, when the machine is heavily loaded, the jobs, once shrunk are not able to expand, so they must be executed all the time with a partition smaller than the job size, thus degrading performance. Thus, at this point the job scheduling policy concentrated just in moldability.Fragmentation was alleviated also by applying backfilling techniques to the job scheduling algorithm. Virtual malleability showed to be an interesting improvement in the window expiring problem. Backfilled jobs even on a smaller partition, can continue execution reducing memory swapping generated by aborts/suspensions In this way the queueing system is prevented from reinserting the backfilled job in the queue and re-executing it in the future

Using Fine-Grained Cycle Stealing to Improve Throughput, Efficiency and Response Time on a Dedicated Cluster while Maintaining Quality of Service

For various reasons, a dedicated cluster is not always fully utilized even when all of its processors are allocated to jobs. This occurs any time that a running job does not use 100% of each of the processors allocated to it. Keeping in mind the needs of both the cluster’s system administrators and its users, we would like to increase the throughput and efficiency of the cluster while maintaining or improving the average turnaround time of the jobs and the quality of service of the “primary” jobs originally scheduled on the cluster. To increase the throughput and efficiency of the cluster, we schedule background jobs to run concurrently with the primary jobs. However, to achieve our goal of maintaining or improving the average turnaround time of the jobs and the quality of service of the primary jobs, we investigate two methods of prioritizing the CPU usage of the primary and background jobs. The first method uses the existing “nice” mechanism in the 2.4 Linux kernel to give background processes a lower priority than primary processes. The second method involves modifying the 2.4 Linux kernel’s CPU scheduler to create a new guest process priority that prevents guest processes from running when primary processes are runnable. Our results come from empirical investigations using real production applications. Production runs using these applications are regularly performed in the dedicated cluster environment that we used for testing. Measurements of various statistics, such as wall time and CPU time, are taken directly from test runs that use these same production applications. This was helpful for comparison to results from models and synthetic applications. We found that using the existing nice mechanism significantly improves the throughput, efficiency and average turnaround time of the cluster but only at the expense of the quality of service of the primary jobs (primary job running times increased 5-25%). On the other hand, we can use the guest process priority to get similar improvements in throughput, efficiency and average turnaround time while not significantly impacting the quality of service of the primary jobs (primary job running times changed less than 1%)

Guaranteed bandwidth implementation of message passing interface on workstation clusters

Due to their wide availability, networks of workstations (NOW) are an attractive platform for parallel processing. Parallel programming environments such as Parallel Virtual Machine (PVM), and Message Passing Interface (MPI) offer the user a convenient way to express parallel computing and communication for a network of workstations. Currently, a number of MPI implementations are available that offer low (average ) latency and high bandwidth environments to users by utilizing an efficient MPI library specification and high speed networks. In addition to high bandwidth and low average latency requirements, mission critical distributed applications, audio/video communications require a completely different type of service, guaranteed bandwidth and worst case delays (worst case latency) to be guaranteed by underlying protocol. The hypothesis presented in this paper is that it is possible to provide an application a low level reliable transport protocol with performance and guaranteed bandwidth as close to the hardware on which it is executing. The hypothesis is proven by designing and implementing a reliable high performance message passing protocol interface which also provides the guaranteed bandwidth to MPI and to mission critical distributed MPI applications. This protocol interface works with the Fiber Distributed Data Interface (FDDI) driver which has been designed and implemented for Performance Technology Inc. commercial high performance FDDI product, the Station Management Software 7.3, and the ADI / MPICH (Argonne National Laboratory and Mississippi State University\u27s free MPI implementation)

3rd EGEE User Forum

We have organized this book in a sequence of chapters, each chapter associated with an application or technical theme introduced by an overview of the contents, and a summary of the main conclusions coming from the Forum for the chapter topic. The first chapter gathers all the plenary session keynote addresses, and following this there is a sequence of chapters covering the application flavoured sessions. These are followed by chapters with the flavour of Computer Science and Grid Technology. The final chapter covers the important number of practical demonstrations and posters exhibited at the Forum. Much of the work presented has a direct link to specific areas of Science, and so we have created a Science Index, presented below. In addition, at the end of this book, we provide a complete list of the institutes and countries involved in the User Forum

Impact of Cache on Data-Sharing in Multi-Threaded Programmes

This thesis answers the question whether a scheduler needs to take into account where communicating threads in multi-threaded applications are executed. The impact of cache on data-sharing in multi-threaded environments is measured. This work investigates a common base-case scenario in the telecommunication industry, where a programme has one thread that writes data and one thread that reads data. A taxonomy of inter-thread communication is defined. Furthermore, a mathematical model that describes inter-thread communication is presented. Two cycle-level experiments were designed to measure latency of CPU registers, cache and main memory. These results were utilised to quantify the model. Three application-level experiments were used to verify the model by comparing predictions of the model and data received in the real-life setting. The model broadens the applicability of experimental results, and it describes three types of communication outlined in the taxonomy. Storing communicating data across all levels of cache does have an impact on the speed of data-intense multithreaded applications. Scheduling threads in a sender-receiver scenario to di↵erent dies in a multi-chip processor decreases speed of execution of such programmes by up to 37%. Pinning such threads to di↵erent cores in the same chip results in up to 5% decrease in speed of execution. The findings of this study show how threads need to be scheduled by a cache-aware scheduler. This project extends the author’s previous work, which investigated cache interference

Performability modelling of homogenous and heterogeneous multiserver systems with breakdowns and repairs

This thesis presents analytical modelling of homogeneous multi-server systems with reconfiguration and rebooting delays, heterogeneous multi-server systems with one main and several identical servers, and farm paradigm multi-server systems. This thesis also includes a number of other research works such as, fast performability evaluation models of open networks of nodes with repairs and finite queuing capacities, multi-server systems with deferred repairs, and two stage tandem networks with failures, repairs and multiple servers at the second stage. Applications of these for the popular Beowulf cluster systems and memory servers are also accomplished. Existing techniques used in performance evaluation of multi-server systems are investigated and analysed in detail. Pure performance modelling techniques, pure availability models, and performability models are also considered. First, the existing approaches for pure performance modelling are critically analysed with the discussions on merits and demerits. Then relevant terminology is defined and explained. Since the pure performance models tend to be too optimistic and pure availability models are too conservative, performability models are used for the evaluation of multi-server systems. Fault-tolerant multi-server systems can continue service in case of certain failures. If failure does not occur at a critical point (such as breakdown of the head processor of a farm paradigm system) the system continues serving in a degraded mode of operation. In such systems, reconfiguration and/or rebooting delays are expected while a processor is being mapped out from the system. These delay stages are also taken into account in addition to failures and repairs, in the exact performability models that are developed. Two dimensional Markov state space representations of the systems are used for performability modelling. Following the critical analysis of the existing solution techniques, the Spectral Expansion method is chosen for the solution of the models developed. In this work, open queuing networks are also considered. To evaluate their performability, existing modelling approaches are expanded and validated by simulations, for performability analysis of multistage open networks with finite queuing capacities. The performances of two extended modelling approaches are compared in terms of accuracy for open networks with various queuing capacities. Deferred repair strategies are becoming popular because of the cost reductions they can provide. Effects of using deferred repairs are analysed and performability models are provided for homogeneous multi-server systems and highly available farm paradigm multi-server systems. Since one of the random variables is used to represent the number of jobs in one of the queues, analytical models for performance evaluation of two stage tandem networks suffer because of numerical cumbersomeness. Existing approaches for modelling these systems are actually pure performance models since breakdowns and repairs cannot be considered. One way of modelling these systems can be to divide one of the random variables to present both the operative and non-operative states of the server in one dimension. However, this will give rise to state explosion problem severely limiting the maximum queue capacity that can be handled. In order to overcome this problem a new approach is presented for modelling two stage tandem networks in three dimensions. An approximate solution is presented to solve such a system. This approach manifests itself as a novel contribution for alleviating the state space explosion problem for large and/or complex systems. When two state tandem networks with feedback are modelled using this approach, the operative states can be handled independently and this makes it possible to consider multiple operative states at the second stage. The analytical models presented can be used with various parameters and they are extendible to consider systems with similar architectures. The developed three dimensional approach is capable to handle two stage tandem networks with various characteristics for performability measures. All the approaches presented give accurate results. Numerical solutions are presented for all models developed. In case the solution presented is not exact, simulations are performed to validate the accuracy of the results obtained