Resource Limits

SLURM scheduling policy support was significantly changed in version 2.0 in order to take advantage of the database integration used for storing accounting information. This document describes the capabilities available in SLURM version 2.0. New features are under active development. Familiarity with SLURM's Accounting web page is strongly recommended before use of this document.

Note for users of Maui or Moab schedulers:
Maui and Moab are not integrated with SLURM's resource limits, but should use their own resource limits mechanisms.

Configuration

Scheduling policy information must be stored in a database as specified by the AccountingStorageType configuration parameter in the slurm.conf configuration file. Information can be recorded in either MySQL or PostgreSQL. For security and performance reasons, the use of SlurmDBD (SLURM Database Daemon) as a front-end to the database is strongly recommended. SlurmDBD uses a SLURM authentication plugin (e.g. MUNGE). SlurmDBD also uses an existing SLURM accounting storage plugin to maximize code reuse. SlurmDBD uses data caching and prioritization of pending requests in order to optimize performance. While SlurmDBD relies upon existing SLURM plugins for authentication and database use, the other SLURM commands and daemons are not required on the host where SlurmDBD is installed. Only the slurmdbd and slurm-plugins RPMs are required for SlurmDBD execution.

Both accounting and scheduling policy are configured based upon an association. An association is a 4-tuple consisting of the cluster name, bank account, user and (optionally) the SLURM partition. In order to enforce scheduling policy, set the value of AccountingStorageEnforce: This option contains a comma separated list of options you may want to enforce. The valid options are

(NOTE: The association is a combination of cluster, account, user names and optional partition name.)
Without AccountingStorageEnforce being set (the default behavior) jobs will be executed based upon policies configured in SLURM on each cluster.
It is advisable to run without the option 'limits' set when running a scheduler on top of SLURM, like Moab, that does not update in real time their limits per association.

Tools

The tool used to manage accounting policy is sacctmgr. It can be used to create and delete cluster, user, bank account, and partition records plus their combined association record. See man sacctmgr for details on this tools and examples of its use.

A web interface with graphical output is currently under development.

Changes made to the scheduling policy are uploaded to the SLURM control daemons on the various clusters and take effect immediately. When an association is deleted, all running or pending jobs which belong to that association are immediately canceled. When limits are lowered, running jobs will not be canceled to satisfy the new limits, but the new lower limits will be enforced.

Policies supported

A limited subset of scheduling policy options are currently supported. The available options are expected to increase as development continues. Most of these scheduling policy options are available not only for a user association, but also for each cluster and account. If a new association is created for some user and a scheduling policy option is not specified the default will be: the option for the cluster/account pair, and if both are not specified then the option for the cluster, and if that also is not specified then no limit will apply.

Currently available scheduling policy options:

The MaxNodes and MaxWall options already exist in SLURM's configuration on a per-partition basis, but the above options provide the ability to impose limits on a per-user basis. The MaxJobs option provides an entirely new mechanism for SLURM to control the workload any individual may place on a cluster in order to achieve some balance between users.

Fair-share scheduling is based upon the hierarchical bank account data maintained in the SLURM database. More information can be found in the priority/multifactor plugin description.

Last modified 10 June 2011