Hyperthreading

License Service supports multiple threads per physical core also referred to as Simultaneous multithreading (SMT) or Hyper-Threading (HT).

Simultaneous multithreading (SMT) or Hyper-Threading (HT) is a technology that facilitates more efficient utilization of your processor's resources by enabling multiple threads to run on a physical core.

For more information, see Intel® Hyper-Threading Technology and Simultaneous Multithreading in Red Hat Enterprise Linux.

License Service supports worker nodes with Hyper-Threading or SMT variants SMT2, SMT4 and SMT8 enabled. For more information about the variants that are supported by IBM Container Licensing rules, see Additional License Counting Guidance for IBM Container licenses in Passport Advantage.

If your IBM software is deployed on a cluster that has SMT or HT enabled, it can significantly change your license costs for this clusters.

Example

The following example shows how Virtual Processor Cores are counted for the worker node with and without Hyper-Threading or SMT enabled.

Scenario: An IBM Cloud Pak® with two bundled products that are licensed with Virtual Processor Core (VPC) is deployed on a cluster that runs on Linux® x86_64. For simplicity, the assumption is that both bundled products are deployed on one worker node with the capacity of 8 Cores.

Table 1. Overall license usage for bundled products
HT/SMT enabled Highest license use for bundled product 1 Highest license use for bundled product 2 Overall license use
No CPU limit: 10 vCPU
Node capacity: 8 vCPU
Capped CPU limit: 8 vCPU
Rounded up value: 8 VPC
CPU limit: 2.5 vCPU
Node capacity: 8 vCPU
Capped PCU limit: 2.5 vCPU
Rounded up value: 3 VPC
11 VPC
Yes: HT HT factor: 2
CPU limit: 10 vCPU
Node capacity: 8 vCPU
Capped CPU limit with HT factor: 4 vCPU
Rounded up value: 4 VPC
HT factor: 2
CPU limit: 2.5 vCPU
Node capacity: 8 vCPU
Capped CPU limit with HT factor: 1.25 vCPU
Rounded up value: 2 VPC
6 VPC
Yes : SMT4 SMT factor: 4
CPU limit: 10 vCPU
Node capacity: 8 vCPU
Capped CPU limit with SMT factor: 2 vCPU
Rounded up value: 2 VPC
SMT factor: 4
CPU limit: 2.5 vCPU
Node capacity: 8 vCPU
Capped CPU limit with SMT factor: 0.625 vCPU
Rounded up value: 1 VPC
3 VPC

Checking if the cluster had multiple threads per physical core is enabled

Before you configure License Service for Hyper-Threading or SMT, make sure that your cluster is enabled for that. Contact your infrastructure provider or read the relevant documentation to check the configuration on the infrastructure level.

Useful links:

Enabling hyperthreading in License Service

License Service supports hyperthreading on worker nodes. If your clusters have SMT or HT enabled, you need to enable hyperthreading in License Service. For instructions, see Enabling hyperthreading.

Hyperthreading in audit snapshot

If the number of threads per core on the cluster is other than 1, which means that hyperthreading is enabled, audit snapshot contains information about hyperthreading on a cluster. The information about the cluster threads per core is included in the data_condition.txt file.

If data_condition.txt file does not include the information about threads_per_core, the number of threads per core on the cluster equals 1, which means that hyperthreading is not enabled.

When you enable and then disable hyperthreading on the cluster, information about threads_per_core that equal 1 remains in the data_condition.txt file. The date that is provided under last updated at implies when hyperthreading was disabled.