dynamic load sharing and balancing sig freund. outline introduction distributed vs. traditional...
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Dynamic Load Sharing and Balancing
Sig Freund
OutlineIntroductionDistributed vs. Traditional
schedulingProcess Interaction modelsDistributed SystemsResearch StudiesGuess about the Future?Questions
IntroductionLoad SharingLoad BalancingStatic vs. Dynamic
Distributed vs. Traditional scheduling differences
Communication overhead is non-negligible
Effects of underlying hardware cannot be ignored
Dynamic behavior of system must be addressed
Process Interaction modelsPrecedence process model
Static Process Scheduling
Precedence Process SchedulingExtended List SchedulingEarliest Task First
Process Interaction modelsCommunication process model
Process Interaction modelsDisjoint process model
Distributed System DifficultiesAssumption of prior knowledge
not realisticUse disjoint process model since
we don’t know how they interact
Simple Heuristic StrategyCentral Controller ProcessMaintain queue size of each
processorProcess arrive and depart
asynchronouslyAssignment made to processor
with shortest queueAt completion, processor sends
queue info
Process MigrationMonitors processors assigned to
processesSchedule is initiated by process
departure instead of arrivalMoves processes to achieve
fairnessTwo common models
◦Sender-initiated algorithm◦Receiver-initiated algorithm
Sender-initiated AlgorithmProcess wishing to off-load
initiatesMigrates process from heavily
loaded processor to lightly loadedRequires three decisions
◦Transfer policy◦Selection policy◦Location policy
Location PolicyRandom selection
◦May cause chain effect of transfersProbe for candidate
◦Probe limit◦Multicast
Receiver-initiated AlgorithmLightly loaded processor requests
more workSame three decisions
◦Transfer policy◦Location policy◦Selection policy
Benefits◦More stable◦Perform better
Research StudiesDynamic load balancing in
distributed computer systems with star topology[1995]
Performance of dynamic load balancing algorithm on cluster of workstations and PCs[2002]
Sender-initiated AlgorithmCompare load balancing policies
for effective dynamic load balancing on the basis of decision strategy for job transfer and destination decision.◦FT◦RT◦ALBCI◦ALBCII
[1995]
Sender-initiated Algorithm
Sender-initiated Algorithm
Hybrid Load Balancing AlgorithmCompare load balancing scheme
for parallel depth first search on two systems.◦6 Sun Workstations running Solaris◦10 PC’s running Linux
Round-robin work sharingCompletely distributed system
[2002]
Hybrid Load Balancing Algorithm
Hybrid Load Balancing Algorithm
Current ChallengesHigh reliance on central nodeHigh load systems require most
communication resourcesHeterogeneous systems greatly
complicate load balancing
Future System[2008]Board of Directors
◦Small group of controlling nodes◦Number is dynamic◦Capable of splitting or combining◦Maintain shared historical data for
better initial process assignmentWorker nodes
◦Specialized functions◦Reconfigurable (Time slice/Com
polling)
References 1.Randy Chow and Theodore Johnson (1997),DISTRIBUTED
OPERATING SYSTEMS AND ALGORITHMS 2. Xinda, M. I. (2002). PERFORMANCE OF LOAD
BALANCING ALGORITHM ON CLUSTER OF WORKSTATIONA AND PCS. Algorithms and Architectures for Parallel Processing, 2002. Proceedings. Fifth International Conference on , (pp. 44-47).
3. Chong-Gun, L. K.-S. (1995). Dynamic load balancing in distributed computer systems with star topology. Distributed Computing Systems, 1995., Proceedings of the Fifth IEEE Computer Society Workshop on Future Trends of , (pp. 514-517).
4. Abraham Silberschatz, Peter Galvin, and Greg Gagne (2005) OPERATING SYSTEM CONCEPTS
5. Sig Freund (2008) FUTURE DISTRIBUTED OPERATING SYSTEM CONCEPT
Questions?