CPU Details - RHEV Test

Excessive usage of physical CPU resources by the RHEV hypervisor or its VMs can be the source of prolonged slowdowns that may be experienced by those VMs. Hence, whenever users complaint of slowdowns in their virtual applications, it would be best to first check whether the hypervisor has adequate unused CPU resources, as a CPU contention can have a disastrous effect on VM performance and consequently application performance. This is why, the eG agent, with the help of its CPU Details - RHEV test, runs periodic usage checks on the CPU resources of the hypervisor. Besides proactively detecting abnormal CPU consumption by the hypervisor, the test also accurately points you to the root-cause of the CPU contention - did it happen because of CPU-hungry VMs on the hypervisor? did it happen because of CPU-hungry user processes or system-level processes? did it occur when the hypervisor performed Kernel Same-Page Merging? or did it happen when the CPU was idle?

Target of the Test: A RHEV Hypervisor

Agent running the test: An internal agent

Output of the test: One set of results for the RHEV hypervisor being monitored.

Configurable parameters for the test
Parameter Description

Test period

How often should the test be executed.


The host for which the test is to be configured.

RHEL MGR Domain,
RHEL MGR Password

To auto-discover the VMs on a target RHEV hypervisor and obtain the outside view of the performance of each VM, the eG agent needs to connect to the RHEV Manager that manages the target RHEV hypervisor. To enable the eG agent to obtain the outside view, you need to configure the test with the following:

  • RHEL MGR Host - The IP address/host name of the RHEV manager that the eG agent should connect to.
  • RHEL MGR Port - The port number at which the said RHEV manager listens.
  • RHEL MGR Domain - The domain to which the RHEV manager belongs.
  • RHEL MGR User and RHEL MGR Password - The credentials of a user with read-only access to the Restful API on the RHEV manager. To know how to create a read-only role and assign it to a user, follow the steps detailed in Configuring the eG Agent to use the RESTful APIs on the RHEV Manager to Obtain the “Outside View”.

If the RHEV hypervisor being monitored was discovered via an RHEV manager, then the IP address, port number, domain name, and user credentials of the RHEV manager used for discovery will be automatically displayed against the respective parameters.

If the RHEV hypervisor being monitored was not discovered via an RHEV manager, but you still want to use an RHEV manager for obtaining the outside view, then, you can select any IP address of your choice from the RHEL MGR host list. By default, this list will be populated with the IP addresses/host names of all the RHEV managers that were configured for the purpose of discovering the RHEV hypervisors. If you select an RHEL MGR host from this list, then the corresponding port number, domain name, and user credentials will be automatically displayed against the respective parameters.

On the other hand, if the RHEV manager that you want to use for metrics collection is not available in the RHEL MGR Host list, then, you can configure an RHEV manager on-the-fly by picking the Other option from the RHEL MGR Host list.  An ADD THE RHEV MANAGER DETAILS window will then pop up. Refer to Configuring an RHEV Manager to Use for Monitoring the RHEV Hypervisor to know how to add an RHEV manager using this window. Once the RHEV manager is added, its IP address, port number, domain name and user credentials will be displayed against the corresponding parameters.

Confirm Password

Confirm the RHEL MGR Password by retyping it here.


If the RHEV manager to which the eG agent should connect is SSL-enabled, then set this flag to Yes. If not, set it to No.

Hypervisor User

Specify the name of a user who has the right to connect to the RHEV hypervisor via SSH.

Hypervisor Password

Specify the password of the Hypervisor User.

Confirm Password

Confirm the Hypervisor Password by retyping it here.

Hypervisor SSH Port

Enter the SSH port at which the RHEV hypervisor listens.

Detailed Diagnosis

To make diagnosis more efficient and accurate, the eG Enterprise embeds an optional detailed diagnostic capability. With this capability, the eG agents can be configured to run detailed, more elaborate tests as and when specific problems are detected. To enable the detailed diagnosis capability of this test for a particular server, choose the On option. To disable the capability, click on the Off option.

The option to selectively enable/disable the detailed diagnosis capability will be available only if the following conditions are fulfilled:

  • The eG manager license should allow the detailed diagnosis capability
  • Both the normal and abnormal frequencies configured for the detailed diagnosis measures should not be 0.
Measurements made by the test
Measurement Description Measurement Unit Interpretation

User CPU utilization

Indicates the percentage of CPU utilized by user processes.


Comparing the value of these measures will enable administrators to figure out where the hypervisor is spending the maximum CPU time - in processing user requests? in system - level processes? or when being idle?

System CPU utilization

Indicates the percentage of CPU resources that the hypervisor utilized for system-level processing.


Idle CPU utilization

Indicates the percentage of CPU time utilized when the hypervisor was idle.


CPU utilization

Indicates the percentage of CPU utilized by the hypervisor.


A high value of this measure is a cause for concern, as it indicates excessive CPU usage by the hypervisor. If left unchecked, it may cause a serious contention for CPU resources amidst VMs.  Use the detailed diagnosis of this measure to know which VMs on the hypervisor are consuming the CPU resources excessively.

Kernel samepage merging CPU utilization

Indicates the percentage of CPU time spent by the hypervisor when performing Kernel Same-page Merging (KSM).


Memory page sharing is supported through a kernel feature called Kernel Same-page Merging (KSM). KSM scans the memory of each virtual machine and where virtual machines have identical memory pages KSM merges these into a single page that is shared between the virtual machines, storing only a single copy. If a guest attempts to change this shared page it will be given it's own private copy. When consolidating many virtual machines onto a host there are many situations in which memory pages may be shared – for example unused memory within a Windows virtual machine, common DLLs, libraries, kernels or other objects common between virtual machines. With KSM more virtual machines can be consolidated on each host, reducing hardware costs and improving server utilization. Use this measure to determine how CPU-intensive KSM is.