Scheduling of Parallel Jobs In a Heterogeneous Multi-Site Environment By Gerald Sabin from Ohio State Reviewed by Shengchao Yu 02/2005

Overview – job scheduling Most research focused on homogeneous multi-site environment Limited research on heterogeneous systems Each job mapped to a single processor Only addressed the scheduling of independent sequential jobs or precedence constrained task graphs where each task is sequential

Problem of the Paper Target system A heterogeneous multi-site environment with each site as a homogeneous cluster of processor, but processors at different sites having different speeds A stream of parallel jobs submitted to a metascheduler

Goal & Approach Goal Find an effective schedule to achieve optimized average turnaround time of the jobs. Basic Approach Extension of proven back-filling based parallel scheduling in single-site scheduling: Multiple (or K) simultaneous requests (MR) Completion-based conservative backfilling Use of Effective Utilization (Efficacy), instead of raw utilization

Extend Backfilling with MR Backfilling – conservative, aggressive Move forward smaller jobs to fill idle process cycles without delaying any jobs with future reservation Multiple Request (MR) Submit each job to multiple sites, and cancel redundant submissions once the job started on one of the sites

Extend Backfilling with MR

Adapt Backfilling to Heter Sys Characteristics on Heter. Sys. The same application performs differently on different sites No site is the fastest on all applications Simple greedy and MR schemes fail Introduction of Efficacy and Effective Utilization Adoption of completion-based conservative backfilling

Introduction of Efficacy and Effective Utilization

Aggressive Vs. Conservative Prefer completion time rather than start time Conservative backfilling chosen Higher Effective Utilization Smaller Average Turnaround time Fig. 6, 7, 8

Aggressive Vs. Conservative

Efficacy Based Scheduling Replace Greedy Policy (FCFS) with Efficacy Use efficacy as the priority order for the jobs in the queue, so that jobs with higher efficacies will attempt to backfill before jobs with lower efficacies In another word, a job will have a greater chance to run on its faster machines.

Efficacy Based Scheduling

Restricted MR Communication Overhead due to Deciding earliest completion time Data transfer for a job Select K sites with best completion time All about compromise Fig 11, 12

Restricted MR

Conclusion Extension of backfilling with the application of MR, Completion time based conservative scheme and Efficacy in a orthogonal fashion A good attempt to optimization across a collection of independent jobs for GRID environment with the characteristics of the heterogeneous system in mind A Heuristic Approach Scalability and Fault-tolerance Sensitivity to the type of applications