Hyperthreading
License Service supports multiple threads per physical core also referred to as Simultaneous multithreading (SMT) or Hyper-Threading (HT).
Important: Enabling HyperThreading will affect only newly calculated license usage data. It will not change historically calculated data. Considering the HyperThreading factor, License Service will not perform any adjustments of license usage accounted and archived prior to the change in License Service configuration.
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.
| 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:
- 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
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