1.9.4 Monitoring the memory resource

This subsection explains how to monitor the memory resource of a logical partitioning feature system.

Organization of this subsection

(1) Overview
(2) Monitoring examples

(1) Overview

In a virtual environment of a system with logical partitioning feature, the hypervisor and each LPAR use memory exclusively allocated to them from the physical memory on the host machine. The amount of memory is specified by the user at the time of building the environment with logical partitioning feature, and exclusively allocated to LPARs.

The hypervisor reserves a fixed amount of memory of 1,280 MB necessary for self-operation, and exclusively allocates the remainder of physical memory to LPARs when they are started (activated). At this time, if sufficient memory is not allocated to LPARs, a low-memory condition occurs, possibly causing performance of the LPARs to deteriorate. In addition, when a LPAR is started (activated), the LPAR fails to start if the amount of memory specified by the user cannot be allocated from the physical memory.

Note that PFM - RM for Virtual Machine cannot capture memory usage, utilization rate, and insufficiency rate data of LPARs. Therefore, you must monitor whether there is a lack of memory in LPARs by using PFM - Agent for Platform or PFM - RM for Platform. When PFM - RM for Virtual Machine is used, if a LPAR runs out of memory, you can take an appropriate corrective action by checking the installed and unused amounts of physical memory on the host machine, and the amount of memory allocated to LPARs.

You can monitor memory resources by using the record shown below. For details about each record, see 5. Records.

PI_HMI record

This record is used to monitor the installed, allocated, and unused amount of physical memory on the host machine, as well as the allocated amount and allocation rate of memory for the hypervisor and for the entire LPAR.

The following figure shows the range of performance data collected in the PI_HMI record.

Figure 1‒98: Correspondence between records and data collection ranges

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(2) Monitoring examples

Using monitoring on the host machine running a virtual environment as an example, this subsection explains the factors that cause insufficient memory resources, and how to solve this problem. The following figure shows the items monitored here and the flow of actions to take.

Figure 1‒99: Monitored items and flow of actions

(a) Example of monitoring the rate of unallocated memory in LPARs

You monitor the rate of unallocated memory in LPARs through a combined use of monitoring templates from PFM - Agent for Platform or PFM - RM for Platform, and monitoring templates from PFM - RM for Virtual Machine.

By monitoring the physical memory usage collected by PFM - Agent for Platform or PFM - RM for Platform (from logical partitioning feature's point of view, it seems to monitor memory usage of LPARs), you can determine which LPAR is running out of memory.

For PFM - Agent for Platform

Monitoring template report to be checked: System Overview
Monitoring template alarm to be checked: Available Memory

Monitoring of the combined report of System Overview above and Host Memory Used from PFM - RM for Virtual Machine enables you to capture the relationship between the LPAR running out of memory and logical partitioning feature.

For PFM - RM for Platform

Monitoring template report to be checked: Memory Used Status
Monitoring template alarm to be checked: Available Memory

Monitoring of the combined report of Memory Usage Status above and Host Memory Used from PFM - RM for Virtual Machine enables you to capture the relationship between the LPAR running out of memory and logical partitioning feature.

(b) Example of monitoring the rate of unallocated memory on the host machine

You can monitor the rate of unallocated memory on the host machine in the Used % field of the PI_HMI record.

The following figure shows an example of monitoring the rate of unallocated memory on the host machine.

Figure 1‒100: Example of monitoring the rate of unallocated memory

Monitoring template report to be checked: Host Memory Used

In this example, you can see that the rate of allocated memory in logical partitioning feature is 80% and 20% of the memory is not used. If there is any unused space, the host machine has an extra amount of memory, which can be reallocated to LPARs running out of memory. If the memory is reallocated, increment the allocation amount of the LPAR running out of memory by 256 MB. Also, reduce the amount of memory allocated to other LPARs without lack of memory.

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