Hello,
Copying to LE 8.2.1's samba shares (external USB device) is painfully slow from macOS 10.12. A 2GB file takes about 10 minutes. Copying the same file from the share to macOS took about 4 minutes. I'm not sure, but I think it was a lot faster in 8.2.0.
When starting to copy, Finder shows 8.4 MB copied for about 4 seconds, then 25.2 MB copied for another 10 seconds and then it goes on with copying.
I set samba log level to 3 and the log is literally flooded with these error messages:
../source3/lib/messages_dgm.c:658(messaging_dgm_out_sent_fragment)
messaging_dgm_out_sent_fragment: messaging_out_queue_recv returned Connection timed out
and
../source3/smbd/smb2_server.c:3102(smbd_smb2_request_error_ex)
smbd_smb2_request_error_ex: smbd_smb2_request_error_ex: idx[5] status[NT_STATUS_NO_SUCH_FILE] 
at ../source3/smbd/smb2_query_directory.c:155
Following some suggestions I found in different forums, I turned off signing by creating an nsmb.conf file under /etc/ with this option:
[default]
signing_required=no
However, this did not have any impact on the speed.
Since I've also seen some locking errors in the log, I set: strict locking = no under [global] in LE (in Configfiles/samba.conf)
Setting SO_SNDBUF=65535 SO_RCVBUF=65535 under socket options actually improved, but it's still pretty slow.
Using SMB2 over SMB3 doesn't seem to change the speed, so it's not related to that.
Does anyone else experience this with macOS?
