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Aggregate Scheduling –
Enhancing Throughput in
Collective Tasking Systems
L. Subramanian
Randy H.Katz
Michael J. Franklin
Collective Tasking Systems
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Properties :–
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Services requests of a predefined set of types
Every request has an associated type
All requests of a particular type can be aggregated into a single request
Bottleneck operation of every type is performed only once for all requests
of that type
Examples:–
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Broadcast disks – application of broadcast scheduling.
Reservation systems – access to the reservation database
Network Provisioning systems – bandwidth brokers
Front-end Database monitors –access point for multiple databases
Disk scheduling systems –locality based access in disks
Caching Systems
Gang Scheduling – Multiprocessor systems
Aggregate Scheduling
Scheduler
application
List of Queues
bottleneck
OPT
Door
Maintainer
Aggregator
List of Queues: A queue of requests for every type
OPT: Aggregate Statistics of requests of every type
Doorkeeper: Triggers event when a new request arrives
Components in an Aggregate
Scheduling System
Aggregator:
• Aggregates requests into types
• Updates OPT data structure
• Informs Maintainer about new event
Scheduler:
• Computes the type with maximum value of OPT function
• Computes Aggregate request for all requests of that type
• Schedules that type to the application
Maintainer:
• Uses an optimization function for types
• Maintains the invariant property of OPT for new events
OPT:
• Data Structure optimized for the optimization metric
• Every optimization metric induces an invariant in OPT
Optimization Metrics
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RxW scheduling
– (#of Requests) * (Max Waiting Time)
Approximate RxW
– Apply RxW for reduced set of types
Kinetic Tournaments
– Total waiting time for requests in a queue
Gang Scheduling
– Associate distance metric between processes (frequency of IPC)
– Schedule group of processes with min value of max distance
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The Cost Dimension
– Cost associated with every type (cost of bottleneck operation)
– Costs can be dynamic (eg. disk scheduling)
– Fagin’s work on fuzzy systems
Other variants
– Bounded queue size (admission control)
– Bounded response time (earliest deadline)
Network Provisioning System
• 12 basic domains in
AT&T’s backbone
• 10% of bandwidth
reserved(statistically)
for VoIP and VPNs.
• A provisioning
system accepts interdomain requests and
reserves along a path.
• All requests between
a pair of domains are
aggregated into a
single request.
• Regulate traffic for
the reserved portion.
Throughput & Block Rate
Characteristics
Response Time Characteristics
Conclusions
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RxW and Kinetic tournaments give much better
performance than FIFO
 RxW vs Kinetic Tournaments(KT)
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RxW has slightly higher throughput than KT
KT has much lesser response time at operating range
Variation of response time in KT is restricted
Max response time of KT is very low (6 times)
RxW has starvation problem
Experiment aggregate scheduling for other
collective tasking systems