Queues and Charges¶

This page details the QOS and queue usage policies. Examples for each type of Cori job are available.

When a job runs on a NERSC supercomputer, charges accrue against one of the user's projects. The unit of accounting for these charges is the "Node Hour", based on the performance of the nodes on Perlmutter. The total number of charged hours for a job is a function of:

• the number of nodes and the walltime used by the job,
• the QOS of the job, and
• the "charge factor" for the system upon which the job was run.

Job charging policies, including the intended use of each queue, are outlined in more detail under "Policies". This page summarizes the limits and charges applicable to each queue.

Selecting a Queue¶

Jobs are submitted to different queues depending on the queue constraints and the user's desired outcomes. Each queue corresponds to a "Quality of Service" (QOS): Each queue has a different service level in terms of priority, run and submit limits, walltime limits, node-count limits, and cost. At NERSC, the terms "queue" and "QOS" are often used interchangeably.

Most jobs are submitted to the "regular" queue, but a user with a particularly urgent scientific emergency may decide to submit to the premium queue for faster turnaround. Another user who does not need the results of this run for many weeks may elect to use the low queue to cut down on costs. And a user who needs fast turnaround while they are using the large telescope could prearrange with NERSC to use the realtime queue for these runs. The user with the scientific emergency will incur a higher-than-regular charge to use the premium queue, while a user who can be flexible about their required runtime is rewarded with a substantial discount.

Assigning Charges¶

Users who are members of more than one project can select which one should be charged for their jobs by default. In Iris, under the "Compute" tab in the user view, select the project you wish to make default.

To charge to a non-default project, use the -A projectname flag in Slurm, either in the Slurm directives preamble of your script, e.g.,

#SBATCH -A myproject

or on the command line when you submit your job, e.g., sbatch -A myproject ./myscript.sl.

Calculating Charges¶

The cost of a job is computed in the following manner: $$ \text{walltime in hours} \times \text{number of nodes} \times \text{QOS factor} \times \text{charge factor} $$.

Charge Factors¶

Charge factors for Allocation Year 2022 are being renormalized around the performance of Perlmutter CPU and GPU nodes.

QOS Cost Factor: Charge Multipliers and Discounts¶

The QOS cost factor is a function of which queue a job runs in. If a job must be urgently run, then a user might submit it to the premium queue, and incur a 2x charge factor. Jobs in the flex queue, on the other hand, receive a substantial discount in exchange for flexibility about walltime.

QOS Limits and Charges¶

Perlmutter GPU¶

• Nodes allocated by a "regular" QOS job are exclusively used by the job.

• Jobs in the preemptible queue can be preempted after two hours. Jobs can be automatically requeued after preemption using the --requeue sbatch flag. See the Preemptible Jobs section for details.

• NERSC's JupyterHub uses the "jupyter" QOS to start Jupyter notebook servers on compute nodes. Other uses of the QOS are currently not authorized, and the QOS is monitored for unauthorized use.

• Jobs may run on the "standard" Perlmutter GPU nodes or on the subset of GPU nodes which have double the GPU-attached memory. To specifically request these higher-bandwidth memory nodes, use -C gpu&hbm80g in your job script instead of -C gpu. Jobs with this constraint must use 256 or fewer nodes.

Perlmutter CPU¶

• Nodes allocated by a "regular" QOS job are exclusively used by the job.

• Even though there is no node limit for the regular queue, not all of the projected 3072 nodes are available today. Please check the state of the nodes in the regular queue with sinfo -s -p regular_milan_ss11

• Jobs in the preemptible queue can be preempted after two hours. Jobs can be automatically requeued after preemption using the --requeue sbatch flag. See the Preemptible Jobs section for details.

• NERSC's JupyterHub uses the "jupyter" QOS to start Jupyter notebook servers on compute nodes. Other uses of the QOS are currently not authorized, and the QOS is monitored for unauthorized use.

Perlmutter Login¶

Cori Haswell¶

Cori KNL¶

JGI Accounts¶

There are 192 Haswell nodes reserved for the "genepool" and "genepool_shared" QOSes combined. Jobs run with the "genepool" QOS uses these nodes exclusively. Jobs run with the "genepool_shared" QOS can share nodes.

Discounts¶

• Big job discount The "regular" QOS charges on Cori KNL are discounted by 50% if a job uses 1024 or more nodes. This discount is available only in the regular QOS for Cori KNL.

  System	Architecture	Big Job Discount	Conditions
  Cori	KNL	0.5	Job using 1024 or more nodes in regular queue

In addition several QOS's offer reduced charging rates:

• The "low" QOS (available on Cori KNL only) is charged 50% as compared to the "regular" QOS, but no extra large job discount applies.

• The "flex" QOS is charged 50% as compared to the "regular" QOS on Haswell and 25% as compared to the "regular" qos on KNL.

• The "overrun" QOS is free of charge and is only available to projects that are out of allocation time. Please refer to the overrun section for more details.