If your file synchronization is too slow in linux, it is most likely due to inotify limit.
Linux typically restricts the amount of watches per user (usually 8192). When you have more directories you need to adjust that number.
On many Linux distributions you can run the following to fix it:
echo "fs.inotify.max_user_watches=204800" | sudo tee -a /etc/sysctl.conf
On Arch Linux and potentially others it is preferred to write this line into a separate file, i.e. you should run:
echo "fs.inotify.max_user_watches=204800" | sudo tee -a /etc/sysctl.d/90-override.conf
This only takes effect after a reboot. To adjust the limit immediately, run:
sudo sh -c 'echo 204800 > /proc/sys/fs/inotify/max_user_watches'