Slurm

Slurm is an open-source cluster management and job scheduler, originally developed at the Lawrence Livermore National Laboratory. Commercial support is now provided by SchedMD. The information provided in this document is a basic guide for some of the most useful commands, along with specific information for the RDHPCS systems. The SchedMD site maintains full documentation and basic tutorials.

Some common Slurm commands are summarized in the table below.

Command	Action/Task
squeue	Show the current queue
sbatch	Submit a batch script
salloc	Submit an interactive job
srun	Launch a parallel job
sinfo	Show node/partition info
sacct	View accounting information for jobs/job steps
sacctmgr	View account information
scancel	Cancel a job or job step
scontrol	View or modify job configuration.

All Slurm commands have on-line manual pages viewable via the man command (e.g., man sbatch) and extensive usage information using the --help option (e.g., sinfo --help). See References for links to the SchedMD documentation.

Running a Job

Computational work on the RDHPCS is performed by jobs. Jobs typically consist of several components:

• A batch submission script

• A binary executable

• A set of input files for the executable

• A set of output files created by the executable

In general, the process for running a job is to:

1. Prepare executables and input files.

2. Write a batch script.

3. Submit the batch script to the batch scheduler.

4. Optionally monitor the job before and during execution.

In addition, users can perform interactive work on the compute nodes using the salloc command.

Batch Scripts

The most common way to interact with the batch system is via batch scripts. A batch script is simply a shell script with added directives to request various resources from or provide certain information to the scheduling system. Aside from these directives, the batch script is simply the series of commands needed to set up and run your job.

To submit a batch script, use the command sbatch myjob.sl.

Consider the following batch script:

#!/bin/bash
#SBATCH -A ABC123
#SBATCH -J RunSim123
#SBATCH -o %x-%j.out
#SBATCH -t 1:00:00
#SBATCH -p hera
#SBATCH -N 1024

cd $MEMBERWORK/abc123/Run.456
cp $PROJWORK/abc123/RunData/Input.456 ./Input.456
srun ...
cp my_output_file $PROJWORK/abc123/RunData/Output.456

In the script, Slurm directives are preceded by #SBATCH, making them appear as comments to the shell. Slurm looks for these directives through the first non-comment, non-whitespace line. Options after that will be ignored by Slurm (and the shell).

Line	Description
1	Shell interpreter line
2	Project to charge
3	Job name
4	Job standard output file (%x will be replaced with the job name and %j with the Job ID)
5	Walltime requested (in HH:MM:SS format). See man sbatch for other formats.
6	Partition (queue) to use
7	Number of compute nodes requested
8	Blank line
9	Change into the run directory
10	Copy the input file into place
11	Run the job ( add layout details )
12	Copy the output file to an appropriate location.

Note

The environment variables used in the above script example are used to indicate locations as specified in Summary of Storage Areas, and are not available on any RDHPCS system.

Interactive Jobs

Most users will find batch jobs an easy way to use the system, as they allow you to “hand off” a job to the scheduler, allowing them to focus on other tasks while their job waits in the queue and eventually runs. Occasionally, it is necessary to run interactively, especially when developing, testing, modifying or debugging a code.

Since all compute resources are managed and scheduled by Slurm, it is not possible to simply log into the system and immediately begin running parallel codes interactively. Rather, you must request the appropriate resources from Slurm and, if necessary, wait for them to become available. This is done through an “interactive batch” job. Interactive batch jobs are submitted with the salloc command. Resources are requested via the same options that are passed via #SBATCH in a regular batch script (but without the #SBATCH prefix). For example, to request an interactive batch job with the same resources that the batch script above requests, you would use salloc -A ABC123 -J RunSim123 -t 1:00:00 -p batch -N 1024. Note there is no option for an output file…you are running interactively, so standard output and standard error will be displayed to the terminal.

Note

At times it will be useful to use a graphical interface (GUI) while running an interactive job, for example a graphical debugger. To allow the interactive job to allow displaying the graphical interface, you must supply the --x11 option to salloc.

Common sbatch Options

There are two ways to specify sbatch options. The first is on the command line when using the sbatch command.

$ sbatch --clusters=<cluster> --account=abc123 myrunScript.sh

The second method is to insert directives at the top of the batch script using #SBATCH syntax. For example,

#SBATCH --clusters=<cluster>
#SBATCH --account=abc123

The two methods can be mixed together. However, options specified on the command line always override options specified in the script.

The table below summarizes options for submitted jobs. Check the Slurm Man Pages for a more complete list.

Option	Example Usage	Description
-A, --account	$SBATCH --account=abc123	Specifies the project to which the job should be charged.
-t, --time	#SBATCH -t 4:00:00	Specify a maximum wall clock limit.
-J, -job-name	#SBATCH -J jobname	Set the name of the job.
-N, --nodes	#SBATCH -N 1024	Request the number of nodes be allocated to a job.
-n, --ntasks	#SBATCH -n 8	Request for a number of total tasks.
--mem	#SBATCH --mem=4g	Specify the real memory required per node
-q, --qos	#SBATCH --qos=normal	Request a quality of service for the job.
-o, --output	#SBATCH --output=jobout.%j	File where the job’s STDOUT will be directed. (%j will be replaced with the job ID.)
-e, --error	#SBATCH --error=joberr.%j	File where the job’s STDERR will be directed. (%j will be replaced with the job ID.) The -o and -e options may reference the same file to have both the STDOUT and STDERR go to the same file.
--mail-user	#SBATCH --mail-user=user@example.com	Email address to be used for notifications.
-M, --clusters	#SBATCH --clusters=cluster_name	Clusters to submit the job to.

Note

Gaea uses a federation of clusters which include the login and dtn cluster (es), the compute clusters (e.g., c5, c6), and the GFDL post processing and analysis cluster (gfdl). On gaea, the --clusters option must be specified, and should be specified for many of the Slurm commands.

Slurm Environment Variables

Slurm reads a number of environment variables, many of which can provide the same information as the job options noted above. We recommend using the job options rather than environment variables to specify job options, as it allows you to have everything self-contained within the job submission script (rather than having to remember what options you set for a given job).

Slurm also provides a number of environment variables within your running job. The following table summarizes those that may be particularly useful within your job (e.g. for naming output log files):

Variable	Description
$SLURM_SUBMIT_DIR	The directory from which the batch job was submitted. By default, a new job starts in your home directory. You can get back to the directory of job submission with cd $SLURM_SUBMIT_DIR. Note that this is not necessarily the same directory in which the batch script resides.
$SLURM_JOBID	The job’s full identifier. A common use for $SLURM_JOBID is to append the job’s ID to the standard output and error files.
$SLURM_JOB_NUM_NODES	The number of nodes requested.
$SLURM_JOB_NAME	The job name supplied by the user.
$SLURM_NODELIST	The list of nodes assigned to the job.

State Codes

A job will transition through several states during its lifetime. Common ones include:

State Code		Description
CA	Cancelled	The job was explicitly cancelled by the user or system administrator
CD	Completed	Job has terminated all processes on all nodes. Exit code of zero.
F	Failed	Job terminated with non-zero exit code or other failure condition.
R	Running	Job currently has an allocation.
TO	Timeout	Job terminated upon reaching its time limit.
PD	Pending	Job is awaiting resource allocation.
OOM	Out Of Memory	Job experienced out of memory error.
NF	Node Fail	The list of nodes assigned to the job.

Job Reason Codes

Reason	Meaning
InvalidQOS	The job’s QOS is invalid.
InvalidAccount	The job’s account is invalid
NonZeroExitCode	The job terminated with a non-zero exit code.
NodeDown	A node required by the job is down.
TimeLimit	The job exhausted its time limit
SystemFailure	Failure of the Slurm system, a file system, the network, etc.
JobLaunchFailure	The job cannot be launched. This may be due to a file system problem, invalid program name, etc.
WaitingForScheduling	The list of nodes assigned to the job.

Job Dependencies

SLURM supports the ability to submit a job with constraints that will keep it running until these dependencies are met. A simple example is where job X cannot execute until job Y completes. Dependencies are specified with the -d option to Slurm.

Flag	Meaning
SBATCH -d after:jobid[+time]	The job can start after the specified jobs start or are cancelled. The optional +time argument is a number of minutes. If specified, the job cannot start until that many minutes have passed since the listed jobs start/are cancelled. If not specified, there is no delay.
SBATCH -d afterany:jobid	The job can start after the specified jobs have ended, regardless of exit state.
SBATCH -d afternotok:jobid	The job can start after the specified jobs terminate in a failed (non-zero) state.
SBATCH -d afterok:jobid	The job can start after the specified jobs complete successfully
SBATCH -d singleton	Job can begin after any previously-launched job with the same name and from the same user have completed. In other words, serialize the running jobs based on username+jobname pairs.

Srun

Your job scripts will usually call srun to run an executable on multiple nodes.

$ srun [OPTIONS... [executable [args...]]]

srun accepts the following options:

Option	Description
-N, --nodes	Number of nodes to use.
-n, --ntasks	Total number of MPI tasks (default is 1).
-c, --cpus-per-task	Logical cores per MPI task (default is 1). When used with --threads-per-core=1, -c is equivalent to physical cores per task.
--threads-per-core	In task layout, use the specified maximum number of hardware threads per core. Must also be set in salloc or sbatch if using --threads--per-core=2.
--ntasks-per-node	If used without -n, requests that a specific number of tasks be invoked on each node. If used with -n, treated as a maximum count of tasks per node.

Heterogeneous Jobs

A heterogeneous job is a job in which each component has virtually all job options available including partition, account and QOS (Quality Of Service). For example, part of a job might require four cores and 4 GB for each of 128 tasks while another part of the job would require 16 GB of memory and one CPU.

To run a heterogeneous job use srun and separate the different components with the colon (:) character. This is similar to mpirun.

srun --ntasks=1 --cpus-per-task=32 ./executable : --ntasks=128 --cpus-per-task=1 ./executable

Monitoring Jobs

The commands squeue, scontrol and scancel from the common slurm commands table will allow users to view, monitor, cancel, and discover information about their jobs on the system.

Show Pending and Running Jobs

Use the squeue command to view a list of current jobs in the queue. See man squeue for more information.

$ squeue -a

To list jobs that belong to a specific user

$ squeue -u <userid>

Show Completed Jobs

Slurm does not keep completed jobs in squeue.

$ sacct -S 2019-03-01 -E now -a

If you don’t specify -S and -E options sacct gives you data from the current day.

Use the sacct command option to list jobs that have run within the last 24 hours and to see their statuses (State). A full list of sacct options and job states can be found on the sacct man page.

$ sacct --user $USER --starttime `date --date="yesterday" +%F` -X --format=JobID,JobName%30,Partition,Account,AllocCPUS,State,Elapsed,QOS

Getting Details About a Job

Slurm only keeps information about completed jobs available via scontrol for 5 minutes after a job completes. After that time, sacct is the way of getting information about completed jobs.

$ scontrol show job <jobid>

Priority and Fairshare

Slurm uses a priority-based scheduling system to allocate resources to jobs. The priority of a job is calculated based on several factors, including the job’s requested resources, the time at which the job was submitted, and any user-defined priority adjustments.

Slurm’s fairshare system is a way of allocating resources based on the historical usage of different users and groups. Fairshare is designed to ensure that resources are distributed fairly over time, so that no one user or group dominates the system.

Understanding Slurm Fairshare

SLURM utilizes a “FairShare” prioritization system. It uses the project’s allocation (RawShares) set by the Portfolio Manager and the RDHPCS Allocation Committee. Slurm normalizes the allocation into a percentage of system priority (Normshares). See definitions below.

Slurm uses various job request parameters (submit time, partition, QOS, job size, requested wall clock time, etc.) and a calculated project’s FairShare Factor (f) to continually assign/adjust the requested jobs’ priority until the job runs.

FairShare is calculated from current allocation information (NormShares) and recent project and system usage data (EffectvUsage) such that more recent usage compared to your allocation and total system usage lowers the project’s FairShare value and less recent usage compared to your allocation and total system usage increases the project’s FairShare.

Fairshare Priority Factor

The fairshare factor serves to prioritize queued jobs such that those jobs charging accounts that are under-serviced are scheduled first, while jobs charging accounts that are over-serviced are scheduled when the machine would otherwise go idle.

Slurm’s fair-share factor is a floating point number between 0.0 and 1.0 that reflects the shares of a computing resource that a user has been allocated and the amount of computing resources the user’s jobs have consumed. The higher the value, the higher is the placement in the queue of jobs waiting to be scheduled.

Slurm on the RDHPCS systems use the Classic Fairshare Algorithm that is calculated by the equation

\[fairshare\_factor = 2^{-(EffectvUsage / NormShares)}\]

A fairshare factor value \(<0.5\) indicates that a project is over utilizing their allocation relative to total system usage, whereas a factor \(>0.5\) indicates the project is underutilized.

Fairshare Definitions

EffectvUsage::

the project’s ProjUsage (RawUsage) divided by the total RawUsage for the system.

NormShares:

the project’s RawShares (allocated core-hours) divided by the total number of RawShares allocated to all projects on the system, or the fraction of the system the project has been allocated, which represents the projects system level priority without regard to QOS and recent usage priority adjustments.

RawShares:

the Core-hours allocation that has been assigned to project1 by the Portfolio Manager as discussed above. Rawshares means little toward job priority until it is compared to the total allocation of the system, which is the next parameter NormShares. Each user of project1 has the RawShare of parent, this means that all the users pull from the total RawShares of project1 and do not have their own individual sub-Shares. Thus all users on project1 have equal access to the full allocation of project1.

RawUsage:

the amount of core-seconds the project has used. RawUsage decays over time scaled linearly by the 1/2 life priority factor that is set for the system, which is currently 5-days (ex. current usage 100%, 5 day old usage 50%, 10 day old usage 25%, etc).

Projects with a windfall allocation always have a FairShare, Normshares, and EffectvUsage of 0 and therefore always have the lowest priority.

Note

Jobs run in the windfall QOS will NOT count toward RawUsage (and EffectvUsage) and hence will not lower FairShare.

Fairshare Reporting

Summary of all accounts

$ sshare

Summary of one account

$ sshare -A <account>

Details by user of one account

$ sshare -a -A <account>

Details by user of all accounts

$ sshare -a

Priority Reporting

As mentioned earlier, Slurm uses multiple factors to determine a job’s priority. The sprio command reports the job’s priority.

$ sprio -j 12345
   JOBID PARTITION   PRIORITY   SITE       AGE   ASSOC  FAIRSHARE        QOS     TRES
   12345 hera        18302014      0   5000000       0    3301977   10000000   cpu=38

Getting Information About Your Projects

The RDHPCS system administrators have supplied additional tools to help the users gather information concerning their jobs, job’s fairshare, and allocation usage. The tools listed in this section may not be available on all RDHPCS systems.

sfairshare

The sfairshare command will show the current FairShare priority status of all projects. Of particular interest will likely be the , the -u option to list just your projects, -w option (these projects always have the lowest priority) to exclude listing windfall projects, and the -T <threshold> option, which will give you a list of all projects and their FairShare value with a higher value than the threshold value you enter. For more options on sfairshare use the sfairshare -h command.

$ sfairshare -w
Project         FairShare       Rank    NormShares      EffUsage
-----------     ----------      ------  ----------      ----------
amb-verif            0.974      23/90      0.00105         0.00004
aoml-hafs1           0.476      70/90      0.13904         0.15884
aoml-osse            0.415      74/90      0.06094         0.08237
aoml-phod            0.503      66/90      0.04483         0.04732
ap-fc                0.963      24/90      0.00435         0.00024
arl                  0.317      85/90      0.00003         0.00006
.
.
.
$ sfairshare -w -T 0.5
Project         FairShare       Rank    NormShares      EffUsage
-----------     ----------      ------  ----------      ----------
amb-verif            0.974      23/90      0.00105         0.00004
aoml-phod            0.503      66/90      0.04483         0.04731
ap-fc                0.963      24/90      0.00435         0.00024
bpe                  1.000      1/90       0.00002         0.00000
ccasm                0.719      44/90      0.00005         0.00003
ccp-mozart           0.552      59/90      0.00042         0.00036
.
.
.

The Slurm sshare command to get project FairShare priority information sorted by Portfolio and sub-Portfolio. Note that Slurm only uses a project’s Fairshare value in priority calculations, not the Portfolio’s or sub-Portfolio’s FairShare.

Note

sfairshare is only available on Hera and Jet.

saccount_params

The saccount_params will show your current:

• Home File System usage/quota (MB)

• For each of your projects

  • Compute: FairShare priority value, (FairShare rank vs all other projects), partition access and available QOS’s for all your projects. Include -l (for long) if you want to see current 30-day allocation, last 30-day usage, and FairShare to 6 digits(saccount_params -l).

  • Scratch disk usage/quota (GB), files on disk and file count quota.

Note

Projects with a windfall allocation of 1 will show an allocation of 0, but you will see the correct Available QOS: windfall. Projects with an allocation of 2 will show an allocation of 1, but you will see the correct Available QOS: Batch, debug, etc.

Note

saccount_params is only available on Hera, Jet, Orion.

$ saccount_params

Account Params -- Information regarding project associations for userid
   Home Quota (/home/userid) Used: 4149 MB Quota: 5120 MB

   Project: projid
      FairShare=1.000 (91/91)
      Partition Access: ALL
      Available QOSes: gpuwf,windfall
      Directory: /scratch[12]/[portfolio]/projid DiskInUse=206372 GB, Quota=255000 GB, Files=5721717, FileQUota=51000000

Generating Reports

Several of the Slurm utilities can be used to generate usage reports. Slurm supplies Sreport. The RDHPCS team supplies Shpcrpt. Both tools can generate similar reports.

See the following for more information:

• Sreport
  • Use Cases
    • Usage Report for Specific Users
    • Usage Report for Account Utilization by User
    • Usage Report for All Users
    • Report Number of Jobs by a User
    • Report Top Usage
  • Report Descriptions and Formats
    • Format Options for Cluster Reports
    • Format Options for Job Reports
  • Time Formats
  • References
• Shpcrpt
  • Use Cases
    • Summary Report
    • Project Usage

References

Further information about Slurm, and the Slurm commands are available using man <command> on all RDHPCS systems, or on the SchedMD documentation site.

• Slurm Documentation

• sacct

• salloc

• sacctmgr

• sbatch

• scancel

• scontrol

• sinfo

• squeue

• srun

• Slurm Fairshare