How can I reduce the consumption of the `vmmem` process?

Daniiel B is on the money. To turn off Vmmem simply go into Powershell or whatever terminal you like to use under admin rights and enter the cmd wsl --shutdown, when your done with playing in wsl1/2.

vmmem even after docker has shut down, will run for a few seconds up to 1 minute before completely shutting off. So try shutting down your containers and docker and it should disappear soon enough.

The accepted answer talks about shutting down WSL (the windows subsystem for Linux) which makes sense if you actually opened and installed a distro, but since you mentioned about Docker, i'm guessing your vmmem is just showing the usage of docker containers only.

Here's a nice explanation from a trustworthy individual : https://devblogs.microsoft.com/oldnewthing/20180717-00/?p=99265