Try btrfs, where with only 5 hours of research you can create a swap file without writing the entire file.
Also there is no other option, the 5h are non-optional.
After doing that twice, In my / now lives
/swapfile-howto``# this is btrfs not a normal file system. # We have to create and allocate the file in a btrfs friendly way, # and tell btrfs to not move or segment it. touch /swapfile999 chmod 600 /swapfile999 truncate -s 0 /swapfile999 chattr +C /swapfile999 fallocate -l 999G /swapfile999 mkswap /swapfile999 swapon /swapfile999 -p 200