http://ggarcia.me/2016/07/12/intellij-inotify-arch.html

To fix the warning about fs.inotify.max_user_watches the IntelliJ shows, it is necessary to set a value for the fs.inotify.max_user_watches and then apply the change.

Here are the commands necessary to fix the issue on ArchLinux:

More information about this can be found in here and in here.

https://confluence.jetbrains.com/display/IDEADEV/Inotify+Watches+Limit