Avoid recompressing modules and firmware
Picking up a suggestion on the ubuntu-devel
mailing list, we can speed up initramfs generation by avoiding the decompression and recompression of already-compressed files like firmware and modules.
Instead, we can gather these files into a second uncompressed CPIO archive and append this to the main, compressed archive.
@daandemeyer also mentioned that mkosi
already does this, and indeed firmware and modules get a separate archive. The code also mentions that a compressed initramfs containing uncompressed modules significantly increases the memory required to boot.