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.
NOTE Hyperthreading is taken into account starting from the date when it was configured. For earlier periods, when hyperthreading was used but was not enabled in License Service, you need to manually divide the values from the audit snapshot by the HT/SMT factor.
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.
| 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 CPU 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:
- Red Hat Customer Portal: How can I tell if Hyperthreading (HT) is enabled on my system?
- Red Hat Customer Portal: What is hyperthreading and how do I configure it?
- Hyperthreading in VMware documentation
- Managing Hyper-V hypervisor scheduler types
- Disabling Intel Hyper-Threading Technology on Amazon Linux
- Azure compute unit (ACU)
- The tools for checking the status of SMT on IBM Power
- Simultaneous multithreading on IBM Z
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
The information about hyperthreading, which is expressed by the
HT/SMT factor and used for calculations in the audit snapshot, can
be verified in the data_condition.txt file. The
data_condition.txt file is a part of the audit
snapshot package.
-
If the
data_condition.txtfile does not include information about HT/SMT factor, the number of threads per core used for calculations equals 1, which means that the hyperthreading feature is not enabled in License Service. -
If the value of HT/SMT factor in the
data_condition.txtfile is other than 1, the hyperthreading feature is enabled in License Service. For example:
HT/SMT:
Factor:
2
Last updated at:
Jan 1, 2025
- If you enable and later disable the hyperthreading feature in
License Service, the information about HT/SMT factor that equals 1
remains in the
data_condition.txtfile. The date that is provided under "Last updated at" implies when the hyperthreading feature was disabled. For example:
HT/SMT:
Factor:
1
Last updated at:
Jan 2, 2025