‘external file changes sync may be slow the current inotify watch limit is too low’

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:

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sudo echo 'fs.inotify.max_user_watches = 524288' >>/usr/lib/sysctl.d/50-default.conf
sudo sysctl -p --system

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

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