Moab Administrator's Guide - Resource Usage Limits

Moab Workload Manager^®

10.4 Resource Usage Limits

10.4.1 Configuring Actions
10.4.2 Specifying Hard and Soft Policy Violations
10.4.3 Constraining Walltime Usage

Resource usage limits constrain the amount of resources a given job may consume. These limits are generally proportional to the resources requested and may include walltime, any standard resource, or any specified generic resource. The parameter RESOURCELIMITPOLICY controls which resources are limited, what limit policy is enforced per resource, and what actions the scheduler should take in the event of a policy violation.

10.4.1 Configuring Actions

The RESOURCELIMITPOLICY parameter accepts a number of policies, resources, and actions using the format and values defined below.

Format

RESOURCELIMITPOLICY <RESOURCE>:[<SPOLICY>,]<HPOLICY>:[<SACTION>,]<HACTION>[:[<SVIOLATIONTIME>,]<HVIOLATIONTIME>]...

Resource Description
CPUTIME maximum total job proc-seconds used by any single job (allows scheduler enforcement of cpulimit)
DISK local disk space (in MB) used by any single job task
JOBMEM maximum real memory/RAM (in MB) used by any single job
JOBPROC maximum processor load associated with any single job
MEM maximum real memory/RAM (in MB) used by any single job task
MINJOBPROC minimum processor load associated with any single job (action taken if job is using 5% or less of potential CPU usage)
NETWORK maximum network load associated with any single job task
PROC maximum processor load associated with any single job task
SWAP maximum virtual memory/SWAP (in MB) used by any single job task
WALLTIME requested job walltime

Policy Description

ALWAYS take action whenever a violation is detected

EXTENDEDVIOLATION take action only if a violation is detected and persists for greater than the specified time limit

BLOCKEDWORKLOADONLY take action only if a violation is detected and the constrained resource is required by another job

Action Description
CANCEL terminate the job
CHECKPOINT checkpoint and terminate job
MIGRATE requeue the job and require a different set of hosts for execution
NOTIFY notify admins and job owner regarding violation
REQUEUE terminate and requeue the job
SUSPEND suspend the job and leave it suspended for an amount of time defined by the X parameter

Example - Notify and then cancel job if requested memory is exceeded

moab.cfg

# if job exceeds memory usage, immediately notify owner
# if job exceeds memory usage for more than 5 minutes, cancel the job

RESOURCELIMITPOLICY MEM:ALWAYS,EXTENDEDVIOLATION:NOTIFY,CANCEL:00:05:00

Example - Checkpoint job on walltime violations

moab.cfg

# if job exceeds requested walltime, checkpoint job
RESOURCELIMITPOLICY WALLTIME:ALWAYS:CHECKPOINT

# when checkpointing, send term signal, followed by kill 1 minute later
RMCFG[base] TYPE=PBS CHECKPOINTTIMEOUT=00:01:00 CHECKPOINTSIG=SIGTERM

Example - Cancel jobs that use 5% or less of potential CPU usage for more than 5 minutes

moab.cfg

RESOURCELIMITPOLICY MINJOBPROC:EXTENDEDVIOLATION:CANCEL:5:00

Example - Migrating a job when it blocks other workload

moab.cfg

RESOURCELIMITPOLICY JOBPROC:BLOCKEDWORKLOADONLY:MIGRATE

10.4.2 Specifying Hard and Soft Policy Violations

Moab is able to perform different actions for both hard and soft policy violations. In most resource management systems, a mechanism does not exist to allow the user to specify both hard and soft limits. To address this, Moab provides the RESOURCELIMITMULTIPLIER parameter which allows per partition and per resource multiplier factors to be specified to generate the actual hard and soft limits to be used. If the factor is less than one, the soft limit will be lower than the specified value and an Moab action will be taken before the specified limit is reached. If the factor is greater than one, the hard limit will be set higher than the specified limit allowing a buffer space before the hard limit action is taken.

In the example below, job owners will be notified by email when their memory reaches 100% of the target and the job will be canceled if it reaches 125% of the target. For wallclock usage, the job will be requeued when it reaches 90% of the specified limit and will be checkpointed when it reaches the full limit.

moab.cfg

RESOURCELIMITPOLICY       MEM:ALWAYS:NOTIFY,CANCEL
RESOURCELIMITPOLICY       WALLTIME:ALWAYS:REQUEUE,CHECKPOINT

RESOURCELIMITMULTIPLIER   MEM:1.25,WALLTIME:0.9

10.4.3 Constraining Walltime Usage

While Moab constrains walltime using the parameter RESOURCELIMITPOLICY like other resources, it also allows walltime exception policies which are not available with other resources. In particular, Moab allows jobs to exceed the requested wallclock limit by an amount specified on a global basis using the JOBMAXOVERRUN parameter or on a per credential basis using the OVERRUN attribute of the *CFG credential parameters.

moab.cfg

JOBMAXOVERRUN    00:10:00
CLASSCFG[debug]  overrun=00:00:30  

# send USR1 signal 5 minutes before job is to be terminated
CLASSCFG[viz]    overrun=00:30:00  PRETERMINATIONSIGNAL=13@00:05:00

10.4 Resource Usage Limits

10.4.1 Configuring Actions

10.4.2 Specifying Hard and Soft Policy Violations

10.4.3 Constraining Walltime Usage

See Also