Activity Monitor showing the virtual machine to take up a lot of RAM in macOS Big Sur

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When checking in the macOS Activity Monitor, a running virtual machine appears to take up about twice as much RAM as it is assigned in the virtual machine settings.

For example, if 6 GB of RAM have been assigned to the virtual machine, Activity Monitor can show it to utilize about 12 GB.

This is a known issue caused by certain peculiarities of how memory allocation is calculated in macOS Big Sur. The actual amount of RAM utilized by the virtual machine is not increased.

A fix will be introduced together with the upcoming macOS Monterey 12 release.

To check an actual amount of RAM allocated to the virtual machine, open Terminal (Applications > Utilities > Terminal) and execute the following command:

for pid in $(ps ax | grep prl_vm_app | grep -v grep | awk '{ print $1 }'); do sudo footprint -p $pid; done

(You will need to enter your Mac password to run the command. No symbols will be shown due to security measures, so just hit the keys and use Return/Enter.)

The command's output will have Footprint: XX MB line, showing the actual amount of memory allocated to the virtual machine.


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