Summary: Implicit Coscheduling:
Coordinated Scheduling with Implicit Information
in Distributed Systems
Andrea Carol Arpaci­Dusseau
Computer Sciences Department
University of Wisconsin -- Madison
Abstract
In modern distributed systems, coordinated time­sharing is required for communicating processes to
leverage the improved performance of switch­based networks and low overhead protocols. Coordinated
time­sharing has traditionally been achieved with gang scheduling or explicit coscheduling, implemen­
tations of which often suffer from many deficiencies: multiple points of failure, high context­switch
overheads, and poor interaction with client­server, interactive, and I/O­intensive workloads.
Implicit coscheduling dynamically coordinates communicating processes across distributed machines
without these structural deficiencies. In implicit coscheduling, no communication is required across op­
erating system schedulers; instead, cooperating processes achieve coordinated scheduling by reacting to
implicit information carried by naturally­occurring communication within the parallel application. The
implementation of this approach is simple and allows participating nodes to act autonomously.
We introduce two key mechanisms in implicit coscheduling. The first component is conditional two­
phase waiting, a generalization of traditional two­phase waiting in which spin­time may be increased
depending upon events that occur while the process spins. The second component is a fair and preemptive

Source: Arpaci-Dusseau, Andrea - Department of Computer Sciences, University of Wisconsin at Madison

Collections: Computer Technologies and Information Sciences