Plan CPU and Memory Allocations

There are two main approaches to modifying resource allocations:

• All resources allocated – You move resources from domains to other domains, and ensure that all resources are allocated.

• Some resources are unallocated – You allocate less than the maximum available cores and memory for a compute node. Any unused cores are considered parked cores and are not counted for licensing purposes. However, parked cores are added to the logical CPU and memory repository. If you have Root Domains, you can later allocate the repository resources to I/O Domains. See Park Cores and Memory.

Depending on which command you use to view domain resources, you might need to convert socket, core, and VCPU values.

1. Identify the resource configuration for each compute node.

   See one of these procedures:

   • Display the Current Domain Configuration (osc-setcoremem)

   • Display the Current Domain Configuration (ldm)

   In this example, one compute node on a SuperCluster M6-32 has two dedicated domains and two Root Domains.

   
   

   Domain Domain Type Cores Memory (GB) primary Dedicated 18 1536 ssccn3-dom1 Dedicated 30 2560 ssccn3-dom2 Root n/a n/a ssccn3-dom3 Root n/a n/a Unallocated Resources 45 4048

2. Add the domain resources together to determine the total number of resources.

   Calculating the total amount of CPU and memory resources gives you a starting point for determining your resource plan.

   While identifying resources, keep these points in mind:

   • Root Domain resources – Are a small amount of resources that are reserved for the exclusive use of Root Domains. Do not factor these resources into your plan.

   • Unallocated resources – These resources are placed in the logical CPU and memory repositories when Root Domains are created, or by leaving some resources unallocated when you use the osc-setcoremem command.

   In this example, the resources for the dedicated domains and the unallocated resources are summed to provide total resources. The Root Domain resources are not included in total resources.

   
   

   Domain Domain Type Cores Memory (GB) primary Dedicated 18 1536 ssccn3-dom1 Dedicated 30 2560 ssccn3-dom2 Root n/a n/a ssccn3-dom3 Root n/a n/a Unallocated Resources 45 4048 Total Resources 93 8144

3. Based on your site requirements, and the type and number of domains on SuperCluster, decide how to allocate CPU and memory for each domain.

   In this example, 12 cores and 1 TB memory are parked from the primary domain, and 18 cores and 1536 GB memory are parked from the ssccn3-dom1 domain.

   The total resources for before and after columns should match. This check ensures that all resources are accounted for in your plan.

   
   

   Domain Domain Type Cores Before Cores After Memory Before (GB) Memory After (GB) primary Dedicated 18 6 1536 512 ssccn3-dom1 Dedicated 30 12 2560 1024 ssccn3-dom2 Root n/a n/a n/a n/a ssccn3-dom3 Root n/a n/a n/a n/a Unallocated Resources 45 4048 Total Resources 93 93 8144 8144

4. Consider your next action:

   • Change resource allocations at the socket granularity level.

     See Change CPU/Memory Allocations (Socket Granularity)

   • Change resource allocations at the core granularity level.

     . See Change CPU/Memory Allocations (Core Granularity)

   • Increase unallocated resources.

     See Park Cores and Memory

Related Information

• osc-setcoremem Overview

• Supported Domain Configurations

• Display the Current Domain Configuration (osc-setcoremem)

• Display the Current Domain Configuration (ldm)

• Change CPU/Memory Allocations (Socket Granularity)

• Change CPU/Memory Allocations (Core Granularity)

• Park Cores and Memory