The Memory (MBps) chart displays virtual machine memory swap rates.

This chart is located in the Home view of the Virtual Machine Performance tab.

Data Counters

Chart Label



Average rate at which memory is swapped into the virtual machine.

Counter: swapinRate

Stats Type: Rate

Unit: MegaBytes per second (MBps)

Rollup Type: Average (Minimum/Maximum)

Collection Level: 1 (4)


Average rate at which memory is swapped out of the virtual machine.

Counter: swapoutRate

Stats Type: Rate

Unit: MegaBytes per second (MBps)

Rollup Type: Average (Minimum/Maximum)

Collection Level: 1 (4)

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 there is sufficient swap space, a high balloon value is not a performance issue. However, if the swapin and swapout values for the host are large, the host is probably lacking the memory required to meet the demand.

If a virtual machine has high ballooning or swapping, check the amount of free physical memory on the host. The host might require more memory resources. If it does not, check the resource shares, reservation, and limit 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 machine.

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

Memory Performance Enhancement Advice




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


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.


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.


If the memory reservation of a 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.


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


Add physical memory to the host.