I was doing a system upgrade on my archlinux and it taked longer than usual. I looked at the download rate it was low. I decided to update my mirrorlist to go faster.
The solution I choose was to use a python program called reflector with the following parameters :
reflector --country France,Germany,Switzerland,Italy,Spain,Netherland,Belgium --protocol https --ipv6 --sort rate -f 5 --save /etc/pacman.d/mirrorlist
It selects the active mirrors near my country that use https and ipv6, it shows the five fastest mirrors ordered by speed and finally it saves them to my pacman config file.
Problem solved ! Thanks Reflector !