Use the vSphere Client memory performance charts to monitor memory usage of clusters, hosts, virtual machines, and vApps. Use the guidelines below to identify and correct problems with memory performance.

To ensure best performance, the host memory must be large enough to accommodate the active memory of the virtual machines. Note that the active memory can be smaller than the virtual machine memory size. This allows you to over-provision memory, but still ensures that the virtual machine active memory is smaller than the host memory.

A virtual machine's memory size must be slightly larger than the average guest memory usage. This enables the host to accommodate workload spikes without swapping memory among guests. Increasing the virtual machine memory size results in more overhead memory usage.

If a virtual machine has high ballooning or swapping, check the amount of free physical memory on the host. A free memory value of 6% or less indicates that the host cannot meet the memory requirements. This leads to memory reclamation which may degrade performance. If the active memory size is the same as the granted memory size, demand for memory is greater than the memory resources available. If the active memory is consistently low, the memory size might be too large.

If the host has enough free memory, check the resource shares, reservation, and limit settings of the virtual machines and resource pools on the host. Verify that the host settings are adequate and not lower than those set for the virtual machines.

If the memory usage value is high, and the host has high ballooning or swapping, check the amount of free physical memory on the host. A free memory value of 6% or less indicates that the host cannot handle the demand for memory. This leads to memory reclamation which may degrade performance.

If memory usage is high or you notice degredation in performance, consider taking the actions listed below.

Memory Performance Enhancement Advice

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Resolution

1

Verify that VMware Tools is installed on each virtual machine. The balloon driver is installed with VMware Tools and is critical to performance.

2

Verify that the balloon driver is enabled. The VMkernel regularly reclaims unused virtual machine memory by ballooning and swapping. Generally, this does not impact virtual machine performance.

3

Reduce the memory space on the virtual machine, and correct the cache size if it is too large. This frees up memory for other virtual machines.

4

If the memory reservation of the virtual machine is set to a value much higher than its active memory, decrease the reservation setting so that the VMkernel can reclaim the idle memory for other virtual machines on the host.

5

Migrate one or more virtual machines to a host in a DRS cluster.

6

Add physical memory to the host.