Time warp operating system

Abstract

This paper describes the Time Warp Operating System, under development for three years at the Jet Propulsion Laboratory for the Caltech Mark III Hypercube multi-processor. Its primary goal is concurrent execution of large, irregular discrete event simulations at maximum speed. It also supports any other distributed applications that are synchronized by virtual time. The Time Warp Operating System includes a complete implementation of the Time Warp mechanism, and is a substantial departure from conventional operating systems in that it performs synchronization by a general distributed process rollback mechanism. The use of general rollback forces a rethinking of many aspects of operating system design, including programming interface, scheduling, message routing and queueing, storage management, flow control, and commitment. In this paper we review the mechanics of Time Warp, describe the TWOS operating system, show how to construct simulations in object-oriented form to run under TWOS, and offer a qualitative comparison of Time Warp to the Chandy-Misra method of distributed simulation. We also include details of two benchmark simulations and preliminary measurements of time-to-completion, speedup, rollback rate, and antimessage rate, all as functions of the number of processors used.

Speculative execution in a distributed file system

“…Time Warp [15] explored how speculative execution can improve the performance of distributed simulations. Time Warp is specialized for executing simulations, and imposes certain restrictions that may be onerous to developers of general applications: processes must be deterministic, cannot use heap storage, and must communicate via asynchronous messages.…”

Simulation-Based Performance Prediction for Large Parallel Machines

“…Its internal state is encapsulated in an object that receives event messages and queues them locally for execution on the internal state. Speculative Synchronization POSE makes use of optimistic concurrency control as in TimeWarp [4]. When an object receives an event, it gets control of the processor.…”

Performance Prediction Using Simulation of Large-Scale Interconnection Networks in POSE

“…As an optimistically-synchronized PDES environment, POSE is based on the Time Warp [10,7] mechanism. POSE uses a variety of adaptive [6] protocols.…”