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“Real-time scheduling of multiple virtual machines
Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
Blekinge Institute of Technology, Faculty of Computing, Department of Computer Science and Engineering.
2017 (English)In: International journal of Computers and their applications, Vol. 24, no 3, p. 91-109Article in journal (Refereed) Published
Abstract [en]

    The use of virtualized systems is growing, and one would like to   benefit from   this   kind   of   systems   also   for   real-time applications  with  hard  deadlines.    There  are  two  levels  of  scheduling  in  real-time  applications  executing  in  a  virtualized  environment: traditional real-time scheduling of the tasks in the real-time  application  inside  a  Virtual  Machine  (VM),  and  scheduling   of   different   VMs   on   the   hypervisor   level.   Traditional real-time scheduling uses methods based on periods, deadlines and worst-case execution times of the real-time tasks.In   order   to   apply   the   existing   theory   also   to   virtualized   environments   we   must   obtain   periods   and   (worst-case) execution times for VMs containing real-time applications.   In this paper, we describe a technique for calculating periods and execution  times  and  utilization  for  VMs  containing  real-time applications with hard deadlines.  We show that when we look at  all  VMs  that  share  a  physical  processor  we  are  able  to  use  longer  (better)  periods.   Alternatively,  if  the  periods  are  the  same,  we  are  able  to  use  a  smaller  amount  of  the  processor  resource  for  the  VMs  and  more  tasks  become  schedulable  compared to when we look at each  VM  in  isolation.   We  also  introduce an overhead model that makes it possible to find VM periods that minimize the processor utilization.

Place, publisher, year, edition, pages
2017. Vol. 24, no 3, p. 91-109
Keywords [en]
Real-time virtual machine;real-time scheduling hard deadlines; VM overhead; VM period
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:bth-15755OAI: oai:DiVA.org:bth-15755DiVA, id: diva2:1173841
Funder
Knowledge Foundation, 20140032Available from: 2018-01-14 Created: 2018-01-14 Last updated: 2018-01-19Bibliographically approved
In thesis
1. Performance Aspects of Databases and Virtualized Real-time Applications
Open this publication in new window or tab >>Performance Aspects of Databases and Virtualized Real-time Applications
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Context: High computing system performance depends on the interaction between software and hardware layers in modern computer systems. Two strong trends that effect different layers in computer systems are that single processors are now more or less completely replaced by multiprocessors, which are often organized into clusters, and virtualization of resources. The performance evaluation of different software on such physical and virtualized resources, is the focus of this thesis.

Objectives: The objectives of this thesis are to investigate the performance evaluation of SQL and No SQL database management systems, namely Cassandra, CouchDB, MongoDB, PostgreSQL, and RethinkDB; and soft real-time application namely, voice-driven web. Scheduling algorithms for resource allocation for hard real-time applications on virtual processor are also investigated.

Methods: Experiment is used to measure the performance of SQL and No SQL management systems on cluster. It is also used to develop a prototype and predicts processor performance of voice-driven web on multiprocessors. Theoretical methods are used to model and design algorithms to schedule real-time applications on the virtual processor machine. Simulation is used to quantify the performance implications of certain parameter values in our theoretical results and to compare expected performance with theoretical bounds in our schedulability tests.

Results:The performance of Cassandra, CouchDB, MongoDB, 2

PostgreSQL, and RethinkDB is evaluated in terms of writing and reading throughput and latencies in cluster computing. For reading throughput, all database systems are horizontally scalable as the cluster’s nodes number increases, however, only Cassandra and couchDB exhibit scalability for data writing. The overall evaluation shows that Cassandra has the most writing scalable throughput as the number of nodes increases with a relative low latency, whereas PostgreSQL has the lowest writing latency, and MongoDB has the lowest reading latency.

The architectures’ tradeoffs of voice-driven web show that the voice engine should be installed on the server instead of being on the mobile device, and performance evaluations show that speech engine scales with respect to the number of cores in the multiprocessor with and without hyperthreading.

The thesis presents scheduling techniques for real-time applications that runs in virtual machines which are time sharing the processor. Each virtual machine’s period and execution time that allow real-time applications to meet their deadlines can be defined using these techniques. Simulation results show the impact of the length of different VM periods with respect to overhead. The tradeoffs between resources consumption and period length are also given. Furthermore, a utilization based test for scheduling real-time application on virtual multiprocessor is presented. This test determines if a task set is schedulable or not. If the task set is schedulable the algorithm provides the priority for each task. This algorithm avoids Dhall’s effect, which may cause task sets with even very low utilization to miss deadlines.

Conclusions: The thesis presented the performance evaluation of reading and writing throughput and latencies for SLQ and NoSQL management systems in the cluster computing. The thesis quantifies the tradeoffs of voice-driven web architectures and the performance scalability of the speech engine with respect to number of cores of the multiprocessor. Furthermore, this thesis proposes scheduling algorithms for real-time 3

application with hard deadline on virtual processors, either as a single core processor or as a multicore processor.

Place, publisher, year, edition, pages
Karlskrona: Blekinge Tekniska Högskola, 2018. p. 36
Series
Blekinge Institute of Technology Doctoral Dissertation Series, ISSN 1653-2090 ; 02
Keywords
SLQ and NoSQL database, Bigdata management systems, Structured and non-structured Database Evaluation, Voice-driven web, Multicore performance prediction, Hard real-time Scheduling, Virtual Multiprocessor Scheduling
National Category
Computer Sciences
Identifiers
urn:nbn:se:bth-15758 (URN)978-91-7295-348-2 (ISBN)
Public defence
2018-09-21, J1650, Blekinge Tekniska Högskola, 371 79 Karlskrona, Karlskrona, 13:00 (English)
Opponent
Supervisors
Funder
Sida - Swedish International Development Cooperation Agency
Available from: 2018-01-15 Created: 2018-01-14 Last updated: 2018-06-07Bibliographically approved

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