https://wiki.archlinux.org/index.php/ext4

core
    e2fsprogs
e4defrag
    e4defrag /some/folder
    e4defrag -c -v /dev/sdxX
    sudo e4defrag -c -v /dev/sda6
    
http://jsmylinux.no-ip.org/performance/using-e4defrag/
http://rus-linux.net/MyLDP/admin/defragment-ext4.html
    0-30% 56%-

community
    shake
http://zenway.ru/page/shake
https://vleu.net/shake/
https://github.com/unbrice/shake

qa
https://superuser.com/questions/536788/do-ext4-filesystems-need-to-be-defragmented

2022
https://linuxrussia.com/file-system-linux-ext4.html