Chapter 24. How do vCPUs, hyper-threading, and subscription structure affect the subscriptions service usage data?
The Red Hat OpenShift portfolio contains offerings that track usage with a unit of measurement of cores, but this measurement is obfuscated by virtualization and multithreading technologies. The behavior of these technologies led to the development of the term vCPUs to help describe the virtual consumption of physical CPUs, but this term can vary in its meaning. In addition, the structure of Red Hat OpenShift offerings can be complex, making usage data in the subscriptions service difficult to understand.
Red Hat has responded to various customer concerns about Red Hat OpenShift usage data through a series of improvements, both to the subscriptions service itself and to the underlying technologies and methodologies that inform Red Hat OpenShift usage tracking.
24.1. Improved calculations for x86-64 architectures with simultaneous multithreading
October 2021: This change assumes that simultaneous multithreading on x86-64 architectures is enabled, resulting in more accurate usage data within the subscriptions service.
Across different technology vendors, the term vCPU can have different definitions. If you work with a number of different vendors, the definition that you use might not match the definition that is used by Red Hat. As a result, you might not be familiar with how Red Hat and the subscriptions service measures usage when vCPUs and simultaneous multithreading (also referred to as hyper-threading) are in use within your environment.
Some vendors offer hypervisors that do not expose to guests whether the CPUs of the guests use simultaneous multithreading. For example, recent versions of the VMware hypervisor do not show the simultaneous multithreading status to the kernel of the VM, and always report threads per core as 1. The effect of this counting method is that customers can interpret the subscriptions service reporting of Red Hat OpenShift usage data related to vCPUs to be artificially doubled.
To address customer concerns about vCPU counting, Red Hat has adjusted its assumptions related to simultaneous multithreading. Red Hat now assumes simultaneous multithreading of 2 threads per core for x86 architectures. For many hypervisors, that assumption results in an accurate counting of vCPUs per core, and customers who use those hypervisors will see no change in their Red Hat OpenShift usage data in the subscriptions service.
However, other customers who use hypervisors that do not expose simultaneous multithreading status to the kernel will see an abrupt change in subscriptions service data in October 2021. Those customers will see their related Red Hat OpenShift usage data in the subscriptions service reduced by 50% on the date that this change in counting is implemented. Past data will not be affected.
Customers who encounter this situation will not be penalized. Red Hat requires that the customer purchase enough subscriptions to cover the usage as counted in the subscriptions service only.
In the past, the discrepancies in the definitions for vCPUs have resulted in known problems with the interpretation of usage and capacity data for some subscriptions service users. This change in the assumptions for simultaneous multithreading is intended to improve the accuracy of vCPU usage data across a wider spectrum of customers, regardless of the hypervisor technology that is deployed.
If you have questions or concerns related to the usage and capacity data that is displayed in the subscriptions service, work with your Red Hat account team to help you understand your data and account status. For additional information about the resolution of this problem, you can also log in to your Red Hat account to view the following issue: Bugzilla issue 1934915.
24.2. Improved analysis of subscription capacity for certain subscriptions
January 2022: These changes improved capacity analysis for subscriptions that include extra entitlements or infrastructure subscriptions. These improvements resulted in a more accurate calculation of usage and capacity data for those subscriptions and a more accurate calculation of the subscription threshold within the subscriptions service for the Red Hat OpenShift portion of your Red Hat account.
- Improved accuracy for subscriptions with numerous entitlements: Certain Red Hat OpenShift subscriptions that included a large capacity of cores also included extra entitlements. These entitlements helped to streamline installation by using tools that rely on attached entitlement workflows. However, these extra entitlements were calculated as extra capacity by the subscriptions service, resulting in confusion about how much Red Hat OpenShift could legally be deployed by customers. As of January 2022, counting methods have been revised to remove the extra entitlements from the capacity calculations.
- Infrastructure subscriptions excluded from capacity calculations: For certain purchases of Red Hat OpenShift subscriptions, a particular type of Red Hat OpenShift infrastructure subscription would be added to that purchase automatically. This type of subscription is used to provide infrastructure support for large deployments. Both version 4.1 and later and version 3.11 subscriptions were affected. Normally for Red Hat OpenShift version 4.1 and later, the subscriptions service does not count infrastructure nodes when calculating your Red Hat OpenShift capacity. However, for accounts that received this infrastructure subscription, the improper calculations were occurring at the subscription level, and that data was passed to the subscriptions service. Red Hat OpenShift capacity numbers were artificially inflated, resulting in an incorrect subscription threshold in the subscriptions service. As of January 2022, an added infrastructure subscription is not considered when calculating your Red Hat OpenShift capacity.
24.3. Isolating Red Hat OpenShift Cluster Manager operational metrics from metrics for the subscriptions service
December 2023 and March 2024: These changes involved analyzing the metrics used by Red Hat OpenShift Cluster Manager for internal operational purposes and determining whether these metrics were still the optimal metrics to use for subscription usage tracking purposes in the subscriptions service. The use of these metrics for two different purposes was determined to be ineffective, and increased the chances for inaccurate subscription usage reporting. Therefore, the subscriptions service changed to a service-level metric that is designed exclusively to track the subscription obligation in cores. The overall assumption for simultaneous multithreading in virtualized, x86 environments at a factor of 2 threads per core remains in effect. For additional information about these changes, see the details in the OCP Cluster Size Corrections Customer Portal article.
