Memory Usage Test

Memory shortage on a host can affect the memory allocation to crucial processes that are being executed on the target host, which in turn can adversely impact the performance of the applications running on the target host. One of the primary reasons for Memory shortage is that of precious memory space being unnecessarily hogged by Modified and Standby memory lists that hold temporary/unused data. The Modified and Standby memory lists cache temporary data when the applications/services run in the target host. These temporary data will no longer be used by the applications/services thus hogging memory space unnecessarily. Therefore, administrators should clear the cached data on a regular basis. If the cached data is not cleared regularly, sometimes, you may not be able to allocate memory to the business-critical processes, which will seriously impact service/application delivery and impair user experience. Therefore, it is imperative that you should closely observe if the memory shortage occurs due to data growth of the Modified and Standby memory lists and proactively initiate remedial actions before it causes severe memory contention on the target host. This can be achieved with the help of the Memory Usage test.

This test periodically monitors the memory usage of the target Windows host, checks whether adequate physical memory is available to the host, and if not, promptly alerts users to the same. In the process, the test also reveals the amount of memory space is abnormally hogged by Modified or Standby memory list. This way, potential memory contention caused due to excessive memory usiliation by the Modified and Standby memory lists is brought to administrator's attention. Besides warning you of memory contention that Modified/Standby memory lists can cause, the test also empowers you to avoid probable memory shortage by initiating automated actions. These automated actions can be closely tracked using detailed diagnostics.

Target of the test : A Windows host system

Agent deploying the test : An internal agent

Outputs of the test : One set of results for the Windows 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. Group Processes with Arguments - By default, this parameter is set to No indicating that this test groups processes of an application only based on their names to list top-10 process groups that consumed memory resources excessively in the detailed diagnosis of the Used physical memory measure. If it is set to Yes, then, this test groups the processes with arguments that are passed to them.

  6. Automated Action Enabled - A memory shortage caused due to memory space hogged by modified and standby memory lists has become an increasingly frequent and critical problem. The memory shortage can make a server stutter or run more slowly than usual. Such operational interruptions can make you spend more time on waiting for pages and programs to load, disturbing your work flow and leading to work delays. Moreover, memory shortage can not only impair user productivity, but can also bring crucial business processes to a halt, and can severely degrade overall user experience with the server. To avoid such an outcome, administrators need to rapidly empty the memory space unnecessarily hogged by the modified and standby memory lists. This way, administrators can ensure that adequate memory is always available for executing business-critical processes.

    To enable administrators to achieve this, eG Enterprise offers 'Automation Actions'. These actions are governed by the 'Automation Action Enabled' flag.

    This flag, if enabled, automatically initiates user-configured actions, so that the memory hogged by modified and standby memory lists can be cleared when memory utilization crosses a configured limit.

    Note:

    The 'Automation Action Enabled' parameters, once configured, will apply only to the chosen component. These settings will not be applied to other components even if the Apply to other components button is clicked in the Specific Test Configuration page.

  7. Automation Memory Limit - This flag appears only if the Automated Action Enabled flag is enabled.

    In this text box, specify the upper limit for memory utilization in percentage beyond which this test should trigger user-configured automation actions. By default, 95 percentage is set against this parameter. When the memory utilization reaches/exceeds the value specified in this text box, the user-configured actions will be automatically triggered. However, you can override this settings if required.

  8. Empty Modified Memory - This flag appears only if the Automated Action Enabled flag is enabled. Modified 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. You can easily clear this memory using the Empty Modified Memory flag.

    By default, this flag is set to No. When this flag is set Yes, amount of memory assigned to the modified list will be automatically cleared if the memory utilization reaches/exceeds the value specified against the Automation Memory Limit parameter.

  9. Empty Standby Memory- This flag appears only if the Automated Action Enabled flag is enabled.

    Standby memory is a page of physical memory that is not actively used. When writing a series of frequently used information in the memory area, the programs and services running on the server will use part of memory as cache. The cache should be released and made available after executing programs and services. If the standby memory is not cleared on a regular basis, it can slow down the server operations. Therefore, it is necessary to clear the standby memory at regular intervals. This can easily done using the Empty Standby Memory flag.

    By default, this flag is set to No. When this flag is set Yes, memory that is allocated to the standby page list will be automatically cleared if the memory utilization reaches/exceeds the value specified against the Automation Memory Limit parameter.

  10. 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.

Cleanup automation status

Indicates the current status of automatic action.

 

The values that this measure can report and their corresponding numeric values are discussed in the table above:

Measure value Numeric value
Not Required 1
Started 2
Running 3
Completed 4
Not Enabled 5
Failed 6

Note:

By default, this measure reports the Measure Values listed in the table above. In the graph of this measure however, the value of this measure is represented using their numeric equivalents only.

Use the detailed diagnosis of this measure to find out what are the automation actions triggered when the memory utilization exceeds the value specified against the Automation Memory Limit parameter.