Memory Usage Test

This test reports statistics related to the usage of the physical memory of the system.

Target of the test : Any host system

Agent deploying the test : An internal agent

Outputs of the test : One set of results for every server being monitored

Configurable parameters for the test
  1. TEST PERIOD - How often should the test be executed
  2. Host - The host for which the test is to be configured
  3. useglance - This flag applies only to HP-UX systems. HP GlancePlus/UX is Hewlett-Packards’s online performance monitoring and diagnostic utility for HP-UX based computers. There are two user interfaces of GlancePlus/UX -- Glance is character-based, and gpm is motif-based. Each contains graphical and tabular displays that depict how primary system resources are being utilized. In environments where Glance is run, the eG agent can be configured to integrate with Glance to pull out detailed metrics pertaining to the memory usage of the HP-UX systems that are being monitored. By default, this integration is disabled. This is why the useglance flag is set to No by default. You can enable the integration by setting the flag to Yes. If this is done, then the test polls the Glance interface of HP GlancePlus/UX utility to report the detailed diagnosis information pertaining to memory usage.
  4. Dynamic Memory Enabled - This flag applies only to the host system that is provisioned from a Microsoft Hyper-V Hypervisor. By default, this flag is set to No. If this flag is set to Yes, then, the eG agent will be able to pull out additional metrics pertaining to the memory usage of the host system provided, Dynamic Memory feature is enabled on the Microsoft Hyper-V Hypervisor through which the host system was provisioned.
  5. 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 system.

GB

 

Used physical memory:

Indicates the used physical memory of the system.

GB

 

Free physical memory:

Memory that does not contain any valuable data, and that will be used first when processes, drivers or Operating System need more memory. This does not include standby memory.

GB

This measure typically indicates the amount of memory available for use by applications running on the target host.

On Unix operating systems (AIX and Linux), the operating system tends to use parts of the available memory for caching files, objects, etc. When applications require additional memory, this is released from the operating system cache. Hence, to understand the true free memory that is available to applications, the eG agent reports the sum of the free physical memory and the operating system cache memory size as the value of the Free physical memory measure while monitoring AIX and Linux operating systems. 

Physical memory utilized:

Indicates the percent usage of physical memory.

Percent

Ideally, the value of this measure should be low. While sporadic spikes in memory usage could be caused by one/more rogue processes on the system, a consistent increase in this value could be a cause for some serious concern, as it indicates a gradual, but steady erosion of valuable memory resources. If this unhealthy trend is not repaired soon, it could severely hamper system performance, causing anything from a slowdown to a complete system meltdown.

You can use the detailed diagnosis of this measure to figure out which processes on the host are consuming memory excessively.

Available physical memory (MB):

Indicates the amount of physical memory, immediately available for allocation to a process or for system use.

GB

Not all of the Available physical memory is Free physical memory. Typically, Available physical memory is made up of the Standby List, Free List, and Zeroed List.

When Windows wants to trim a process' working set, the trimmed are moved (usually) to the Standby List. From here, they can be brought back to life in the working set with only a soft page fault (much faster than a hard fault, which would have to talk to the disk). If a page stays in the standby List for a long time, it gets freed and moved to the Free List.

In the background, there is a low priority thread (actually, the only thread with priority 0) which takes pages from the Free List and zeros them out. Because of this, there is usually very little in the Free List.

All new allocations always come from the Zeroed List, which is memory pages that have been overwritten with zeros. This is a standard part of the OS' cross-process security, to prevent any process ever seeing data from another. If the Zeroed List is empty, Free List memory is zeroed and used or, if that is empty too, Standby List memory is freed, zeroed, and used. It is because all three can be used with so little effort that they are all counted as "available".

A high value is typically desired for this measure.

This measure will be available for Windows hosts only.

Modified memory:

Indicates the amount of memory that is allocated to the modified page list.

MB

This memory contains cached data and code that is not actively in use by processes, the system and the system cache. This memory needs to be written out before it will be available for allocation to a process or for system use.

Cache pages on the modified list have been altered in memory. No process has specifically asked for this data to be in memory, it is merely there as a consequence of caching. Therefore it can be written to disk at any time (not to the page file, but to its original file location) and reused. However, since this involves I/O, it is not considered to be Available physical memory.

This measure will be available for Windows hosts only.

Standby memory:

Indicates the amount of memory assigned to the standby list.  

MB

This memory contains cached data and code that is not actively in use by processes, the system and the system cache. It is immediately available for allocation to a process or for system use. If the system runs out of available free and zero memory, memory on lower priority standby cache page lists will be repurposed before memory on higher priority standby cache page lists.

Typically, Standby memory is the aggregate of Standby Cache Core Bytes,Standby Cache Normal Priority Bytes, and Standby Cache Reserve Bytes. Standby Cache Core Bytes is the amount of physical memory, that is assigned to the core standby cache page lists. Standby Cache Normal Priority Bytes is the amount of physical memory, that is assigned to the normal priority standby cache page lists. Standby Cache Reserve Bytes is the amount of physical memory, that is assigned to the reserve standby cache page lists.

This measure will be available for Windows hosts only.

Cached memory:

This measure is an aggregate of Standby memory and Modified memory.

MB

This measure will be available for Windows hosts only.

Maximum memory allocated

Indicates the maximum amount of memory that the host system is allowed to use.

MB

This measure will be available only for Windows hosts that are provisioned from a Microsoft Hyper-V Hypervisor.

Memory usage by maximum allocated memory

Indicates the percentage of memory that is utilized from the maximum amount of memory that the host system is allowed to use.

Percent

This measure will be available only for Windows hosts that are provisioned from a Microsoft Hyper-V Hypervisor.