guest outbound connections bandwidth limited

[agepee]

hi,
i have unraid running as a guest with a virtio network adapter.
running iperf i get about 30 gbit/s from host to guest.

[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec  4.79 GBytes  41.2 Gbits/sec  218   2.51 MBytes
[  5]   1.00-2.00   sec  4.78 GBytes  41.1 Gbits/sec    0   2.51 MBytes
[  5]   2.00-3.00   sec  4.84 GBytes  41.6 Gbits/sec    0   2.51 MBytes
[  5]   3.00-4.00   sec  4.58 GBytes  39.3 Gbits/sec    0   2.51 MBytes
[  5]   4.00-5.00   sec  4.74 GBytes  40.7 Gbits/sec    0   2.51 MBytes
[  5]   5.00-6.00   sec  4.75 GBytes  40.8 Gbits/sec    0   2.51 MBytes
[  5]   6.00-7.00   sec  4.70 GBytes  40.3 Gbits/sec    0   2.51 MBytes
[  5]   7.00-8.00   sec  4.57 GBytes  39.2 Gbits/sec    0   2.51 MBytes
[  5]   8.00-9.00   sec  4.58 GBytes  39.4 Gbits/sec    0   2.51 MBytes
[  5]   9.00-10.00  sec  4.70 GBytes  40.4 Gbits/sec    0   2.51 MBytes
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  47.0 GBytes  40.4 Gbits/sec  218             sender
[  5]   0.00-10.00  sec  47.0 GBytes  40.4 Gbits/sec                  receiver

guest to host is limited to 700-900 mbit/s per connection with a multi-gbit peak at the start.
[ ID] Interval Transfer Bitrate Retr Cwnd [ 5] 0.00-1.00 sec 710 MBytes 5.95 Gbits/sec 0 272 KBytes [ 5] 1.00-2.00 sec 100 MBytes 839 Mbits/sec 0 272 KBytes [ 5] 2.00-3.00 sec 88.8 MBytes 745 Mbits/sec 0 272 KBytes [ 5] 3.00-4.00 sec 88.8 MBytes 744 Mbits/sec 0 277 KBytes [ 5] 4.00-5.00 sec 91.2 MBytes 765 Mbits/sec 0 266 KBytes [ 5] 5.00-6.00 sec 90.0 MBytes 755 Mbits/sec 0 269 KBytes [ 5] 6.00-7.00 sec 91.2 MBytes 765 Mbits/sec 0 280 KBytes [ 5] 7.00-8.00 sec 88.8 MBytes 744 Mbits/sec 0 269 KBytes [ 5] 8.00-9.00 sec 90.0 MBytes 755 Mbits/sec 0 269 KBytes [ 5] 9.00-10.00 sec 88.8 MBytes 744 Mbits/sec 0 266 KBytes - - - - - - - - - - - - - - - - - - - - - - - - - [ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 1.49 GBytes 1.28 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 1.49 GBytes 1.28 Gbits/sec receiver

running multiple threads i can get up to 30-40 gbit/s. with single connections running ABOVE 1 gbit/s as desired.
[ ID] Interval Transfer Bitrate Retr [ 5] 0.00-10.00 sec 4.51 GBytes 3.87 Gbits/sec 0 sender [ 5] 0.00-10.00 sec 4.50 GBytes 3.87 Gbits/sec receiver [ 7] 0.00-10.00 sec 4.52 GBytes 3.89 Gbits/sec 0 sender [ 7] 0.00-10.00 sec 4.52 GBytes 3.88 Gbits/sec receiver [ 9] 0.00-10.00 sec 4.67 GBytes 4.01 Gbits/sec 0 sender [ 9] 0.00-10.00 sec 4.66 GBytes 4.00 Gbits/sec receiver [ 11] 0.00-10.00 sec 4.79 GBytes 4.12 Gbits/sec 0 sender [ 11] 0.00-10.00 sec 4.79 GBytes 4.11 Gbits/sec receiver [ 13] 0.00-10.00 sec 4.82 GBytes 4.14 Gbits/sec 0 sender [ 13] 0.00-10.00 sec 4.82 GBytes 4.14 Gbits/sec receiver [ 15] 0.00-10.00 sec 2.32 GBytes 1.99 Gbits/sec 0 sender [ 15] 0.00-10.00 sec 2.32 GBytes 1.99 Gbits/sec receiver [ 17] 0.00-10.00 sec 4.87 GBytes 4.18 Gbits/sec 0 sender [ 17] 0.00-10.00 sec 4.86 GBytes 4.18 Gbits/sec receiver [ 19] 0.00-10.00 sec 4.79 GBytes 4.11 Gbits/sec 0 sender [ 19] 0.00-10.00 sec 4.78 GBytes 4.11 Gbits/sec receiver [SUM] 0.00-10.00 sec 35.3 GBytes 30.3 Gbits/sec 0 sender [SUM] 0.00-10.00 sec 35.3 GBytes 30.3 Gbits/sec receiver

there is no tuning happening on the unraid side and cpu usage on host and guest is low (no cores/threads pegged) during the the tests.
any tips?

EDIT:
after disabling the network bridge in unraid i can get good bandwidth between host and guest in either direction... now its smb that is limited to ~700-800 mbit/s from guest to host. HELP?
EDIT2:
transfer from host to guest is going full speed. only from guest to host is limited somehow.