Memory Details - RHEV Test

A contention for memory resources on the RHEV hypervisor can affect the memory allocation to VMs, which in turn can adversely impact the performance of the applications operating on the VMs. It is therefore imperative that you closely observe how the hypervisor uses the physical memory available to it, so that you can proactively determine a potential memory crunch. This can be achieved with the help of the Memory Details - RHEV test. This test periodically monitors the memory usage of the hypervisor, checks whether adequate free memory is available to the hypervisor, and if not, promptly alerts users to the same. In the process, the test also reveals the top memory VMs executing on the hypervisor, checks swap memory usage, and also reports whether/not memory has been overcommitted by the hypervisor. This way, the test also points you to the probable reasons for the memory erosion (if any) - is it owing to memory-starved VMs on the hypervisor? or is it because the hypervisor has overcommitted memory?

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.
Host	The host for which the test is to be configured.
RHEL MGR Host, RHEL MGR Port, RHEL MGR Domain, RHEL MGR User 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.
SSL	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.
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

Total physical memory

Indicates the total physical memory of the RHEV hypervisor.

Free physical memory

Indicates the amount of physical memory currently unused on the hypervisor.

Ideally, the value of this measure should be high. A low value or a consistent decrease in this value could indicate a gradual memory erosion, which can consequently affect the host as well as VM performance.

Used physical memory

Indicates the amount of physical memory currently being utilized by the hypervisor.

Ideally, the value of this measure should be low. A very high value or a value that grows dangerously close to the Total physical memory of the host is a cause for concern.

Memory overhead

Indicates the memory overhead on the hypervisor.

The value of this measure is typically the difference between the Total physical memory and the sum of the Used physical memory and the Free physical memory measures.

Physical memory usage

Indicates the percentage of total physical memory that is being used by the hypervisor.

Percent

Ideally, the value of this measure should be low. A high value or a value close to 100% indicates a contention for memory resources on the hypervisor. Use the detailed diagnosis of this measure to know the memory configuration of each VM on the RHEV hypervisor, and the how every VM is using the configured memory. Memory-hungry VMs can thus be isolated.

Physical memory free

Indicates the percentage of percentage of total physical memory that is currently free on the hypervisor.

Percent

Ideally, the value of this measure should be high. A low value or a consistent decrease in this value indicates a contention for memory resources on the hypervisor.

I/O memory buffers

Indicates the total I/O memory buffers in the hypervisor.

Cached memory

Indicates the total OS cached memory in the RHEV hypervisor.

Total swap memory

Indicates the total amount of swap memory on the hypervisor.

Free swap memory

Indicates the amount of swap memory that is currently unused on the hypervisor.

A high value is desired for this measure, as a consistent decrease in this value is a sign of excessive swap usage, which in turn signals a memory bottleneck.

Used swap memory

Indicates the amount of swap memory that is currently utilized by the hypervisor.

Significant or consistent memory swapping indicates that the hypervisor is severely overcommitted and that performance degradation is imminent or actively occurring.

Cached swap memory

Indicates the total swap memory that the hypervisor has cached.

Swap memory usage

Indicates the percentage of swap memory used by the hypervisor.

Percent

A high value is indicative of a contention for memory resources on the hypervisor.

Is memory overcommitted?

Indicates whether the hypervisor memory is overcommitted or not.

Is memory overcommitted?

Indicates whether the hypervisor memory is overcommitted or not.

Hypervisor memory is over-committed when the total memory space allocated (memory granted) to powered-on VMs, plus hypervisor memory overhead, is greater than the amount of total physical memory available to the host. A severe memory overcommitment can cause serious performance degradations.

If the value of this measure is Yes, it indicates that the hypervisor memory is overcommitted. The value No indicates that there is no overcommitment of memory.

The numeric values that correspond to these measure values are indicated in the table below:

Measure Value	Numeric Value
Yes	1
No	0

Note:

By default, this measure reports one of the Measure Values listed in the table above. The graph of this measure however will represent the memory overcommitment status using the numeric equivalents - ‘0’ or '1’.