Why BTRFS doesn't offer live deduplication as ZFS?

[tlaurion]

Really high level question, I know. Really appreciate this project, but can't stop thinking that if the hash table was managed by the kernel, async (AIO) was used in kernel to spool the writes and check extends prior of write, the initial write could be deduped instead of being rewritten?

I guess this would add way to much delays to be implemented inside of the kernel as ZFS does? (Not tested but plan doing so on top of QubesOS since they now ship dom0 requirements for dom0, while installer doesn't permit ZFS partitioning and pool creation so templates and qubes are created in stage2 install as for BTRFS).

Was interested in reading your thoughts on why BTRFS doesn't offer live deduplication and only offline deduplication, which bees permits. Thanks!