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Scheduler Basics. Juli Rew CISL User Forum May 19, 2005. IBM Scheduling Life of a Job Submit Filter Batch Priority Scheduler Factors Affecting BPS Job Scheduling LoadLeveler Load Sharing Facility Scheduling • LSF Scheduling on Linux Systems

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Scheduler basics

Scheduler Basics

Juli Rew

CISL User Forum

May 19, 2005


IBM Scheduling

Life of a Job

Submit Filter

Batch Priority Scheduler

Factors Affecting BPS Job Scheduling


Load Sharing Facility Scheduling

• LSF Scheduling on Linux Systems

Differences from IBM Scheduling


Ibm scheduling life of a job

IBM Scheduling: Life of a Job



Submit Filter

Requirements Processing


Job Ordering


Job Execution

Requirements Not Met

Reject Job

Build Ordered

List of Jobs

Job Starts

Requirements Problem

Staff Rejects Job

Job Completes




Submit filter features

Checks the LoadLeveler job script for:

- valid parameters

- valid queue name

- consistent combinations of features, eg., shared/not_shared, tasks_per_node/node options

Moves jobs with allocation holds to hold queues

Moves jobs with cutoff projects to standby queue

Submit Filter Features

Batch priority job scheduler features

Written at NCAR

Orders jobs based on policy

Creates separate facilities (Community, Climate System Laboratory)

Further separates jobs into proposal groups (NCAR/UNIV, CCSM/oCSL)

Hands the final order list to LoadLeveler

Allows for backfilling of jobs to avoid idle resources

Batch Priority Job Scheduler Features

Bluesky queue priorities

Bluesky Queue Priorities

Prioritization of jobs by bps

all_spec jobs run with the highest priority and can access all nodes

Below that, all com and csl jobs divided equally

Round Robin by Group/User




com csl

\ /

top job

50-50% split not hard

Prioritization of Jobs by BPS

Other factors affecting job scheduling

Backfilling - Jobs that will not interfere with start of highest priority job allowed to slip in

- Sweet spot: < 3 hours and small node count

Allocation Holds - Job flagged if a project/division exceeds its 30-day or 90-day allocation thresholds

- H1 and H2 jobs reordered at a priority above standby but below non-flagged jobs

Special Initiatives - Nodes reserved for real-time or other special runs

Other Factors Affecting Job Scheduling

Documentation and utilities

batchview command gives snapshot of current ordering

Basic information on scheduling given at

Documentation and Utilities


IBM's batch control job system

Allows jobs to be started, stopped, or cancelled

Controls allocation of resources (CPU, memory)

Allows custom scheduler plug-in (e.g., BPS)

Two mutually-exclusive options: LoadLeveler scheduler or custom scheduler.


Load sharing facility

Commercial product from Platform Computing

Currently being used on major Linux platforms

Also available for IBM, but still in evaluation

Ability to do Hierarchical Fair-Share Scheduling with Backfill, based on same facility scheme used in BPS

Community/CSL facility division implemented implicitly within the scheduler rather than explicitly by queue name

• Can schedule among multiple platforms - "Grid”

Load Sharing Facility



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