I installed Gnome Manjaro on a BTRFS partition. According to the Manjaro Swap manual page, if the partition is BTRFS, I should run some special commands to disable compression and COW for the swap file. That made me wonder if I don’t do that, Manjaro enables compression by default. I read the BTRFS compression page and it looked like that I need to enable compression with a special mounting parameter, but of course, I did not do such thing; all I did was selecting BTRFS in Manjaro’s GUI installer. So, I am not sure why the Manjaro manual tells me to disable compression for swap file.
Well then check fstab:
Zstd compression by default