What is hyper-threading?
Hyper-threading is a hardware innovation that allows a Physical CPU to split its physical cores into virtual cores, also known as threads. This helps the CPU to perform multiple tasks simultaneously, increasing performance. This technology was first implemented by Intel and now being used by different chip manufacturers.
Hyper-threading is heavily used in virtualization, to present multiple virtual cores on the virtual machines running on the same set of physical cores.
Figure 1 Hyper-threading enabled on Physical Machine
Virtualization for both on-premise provided by vendors such as VMware ESX, Microsoft Hyper-V and Virtual machines provided by cloud providers such as MS Azure and AWS rely heavily on hyper-threading to provide optimized results.
Figure 2 AWS Virtual Machines Type with Hyper-threading enabled
Hyper-threading not only has implications on improving server performance but has a major role to play in terms of software licensing for major software products such as Microsoft SQL Server, Oracle DB server, etc.
For example,
- Licensing Oracle DB on AWS/Azure: count two vCPUs as equivalent to one Oracle Processor license if hyper-threading is enabled, and one vCPU as equivalent to one Oracle Processor license if hyper-threading is not enabled.
- Licensing MS SQL Server on virtual machines states that when licensing virtual machines, license the virtual processors used by the virtual machines, with a minimum of 4 Core licenses per virtual machine
Hence, it is imperative that the cores (or virtual cores) used by virtual machines are discovered.
How does ServiceNow support hyper-threading?
ServiceNow Discovery discovers all required attributes for virtual cores i.e.
Virtual cores available to a virtual machine or vCPU = CPU Core count*CPU Count*CPU Core thread
Figure 3 Hyper-threading Attributes discovered by ServiceNow Discovery
These attributes are automatically discovered by ServiceNow Discovery for virtual machines on-premise, as well as the cloud (including IaaS and PaaS) resources. Please note that if CPU Core thread > 1 it means that hyper-threading is enabled.
The vCPU values need not be counted. ServiceNow Discovery automatically determines the vCPU or virtual core values on virtual machines. For example, one can see the Number of vCPU=2 on an AWS Virtual machine.
Figure 4 AWS Virtual machine with vCPU=2
This is automatically discovered and populated on ServiceNow CMDB virtual machine table under the CPU Column. Note, that the CPU value on ServiceNow and the vCPU values on AWS have a perfect match.
Figure 5 vCPU value discovered on ServiceNow
ServiceNow Discovery not only supports hyper-threading discovery on virtual machines hosted on Cloud (i.e. AWS, Azure, etc.) but can also discover these values for on-premise virtualization technologies such as VMWare ESX. As you can see the hyper-threading flag is automatically discovered on ESX servers, indicating if hyper-threading is enabled or not.
Figure 6 Hyperthreading Enabled on VMware ESX Machine on ServiceNow
Once ServiceNow Discovery discovers these attributes, ServiceNow SAM makes use of these attributes in the reconciliation engine to arrive at an accurate license compliance position.
Author: Srinivas Ramanujaiah
