Slurm

Getting Started with Slurm in ExCL with best practice recommendations.

Getting Started with Slurm

For general Slurm use and reference, see Job Submission with Slurm - CADES User Documentation, CADES Cheat Sheet, and Cheat Sheet | ExCL User Docs.

sbatch Template

Here is a recommended Slurm sbatch script template:

#!/bin/bash

#SBATCH --job-name=test
#SBATCH --mail-type=END,FAIL
#SBATCH --mail-user=[e-mail]
#SBATCH --nodes=1
#SBATCH --ntasks=1
#SBATCH --cpus-per-task=1
#SBATCH --output=slurm-test-out.txt
#SBATCH --error=slurm-test-err.txt
#SBATCH --partition=compute
#SBATCH --nodelist=justify

GIT_ROOT=$(git rev-parse --show-toplevel)
SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )

echo Started: $(date)
echo Host: $(hostname)
echo Path: $(pwd)
echo --------------------------------------------------------------------------------

### Setup Environment

### Run Command
echo Run Task

echo --------------------------------------------------------------------------------
echo Finished: $(date)

Using the Preemptable GPU Queue (nvidia-long)

The nvidia-long queue provides opportunistic GPU access for long-running or flexible workloads. Jobs in this queue may be preempted when higher-priority work arrives.

Preemption allows better overall cluster utilization, but your job must be written to tolerate interruption.

---

What “Preemptable” Means

Jobs submitted to nvidia-long:

• Run when GPUs are idle

• May be stopped at any time

• Are requeued instead of canceled only if you request it

• May restart multiple times

The normal GPU queue (nvidia) is not preempted.

---

Important Cluster Policy

The cluster is configured with:

PreemptType=preempt/partition_prio
PreemptMode=REQUEUE
JobRequeue=0

What this means for users

• Preemption is enabled

• Preempted jobs are eligible to be requeued

• Jobs are NOT requeueable by default

• You must explicitly request requeue behavior

If you do not request requeue:

• Your job will be canceled when preempted

• Partial work will be lost

---

Submitting a Preemptable Job

Basic submission

sbatch -p nvidia-long my_job.sh

⚠️ This job will be canceled on preemption unless you also add --requeue.

---

Making Your Job Requeueable (REQUIRED)

To allow your job to be restarted after preemption, you must include:

#SBATCH --requeue

Example job script

#!/bin/bash
#SBATCH -p nvidia-long
#SBATCH --requeue
#SBATCH --job-name=my-long-job
#SBATCH --time=7-00:00:00
#SBATCH --gres=gpu:1

./run_my_workload.sh

---

Handling Preemption Gracefully (Strongly Recommended)

When a job is preempted, Slurm sends a SIGTERM signal before stopping it.

You should:

• Catch the signal

• Save checkpoints

• Exit cleanly

Example with signal handling

#!/bin/bash
#SBATCH -p nvidia-long
#SBATCH --requeue
#SBATCH --signal=B:TERM@60   # 60 seconds warning

checkpoint() {
    echo "Preempted – saving state..."
    ./save_checkpoint.sh
    exit 0
}

trap checkpoint SIGTERM

./run_my_workload.sh

This gives your job 60 seconds to checkpoint before requeue.

---

How Requeued Jobs Behave

When a requeueable job is preempted:

• It transitions to PENDING (BeginTime)

• Slurm may delay restart briefly to avoid thrashing

• scontrol show job will show:

  • Restarts=1 (or higher)

  • Requeue=1

This is expected behavior.

---

Monitoring Preemptable Jobs

Check job status

squeue -j <jobid>

See restart count

scontrol show job <jobid> | grep -i restart

View job history

sacct -j <jobid> --format=JobID,State,Reason,Elapsed

---

When to Use nvidia-long

Good fits

• Parameter sweeps

• Model training with checkpoints

• Monte Carlo workloads

• Long experiments without strict deadlines

Not recommended

• Jobs that cannot restart

• Short, latency-sensitive runs

• Jobs without checkpointing

---

Summary

Queue	Preemptable	Requires --requeue	Intended Use
nvidia	❌ No	N/A	Normal GPU jobs
nvidia-long	✅ Yes	✅ Yes	Opportunistic / long jobs

Key takeaways

• ✔ nvidia-long jobs can be interrupted

• ✔ Always use --requeue if you want your job restarted

• ✔ Handle SIGTERM and checkpoint frequently

• ✔ Expect jobs to restart multiple times