Low performance of BBR compared to cubic

Hi,

While test TCP RACK functions, I tested BBR BTW.

This is a quick test with iperf3 on bare metal ( old MBP i5 2 cores 4 threads ).
The kernel current/15 with debug options disabled. Following is the performance result:

freebsd:	37.2 Gbits/sec	1.32 MBytes
RACK:		27.9 Gbits/sec	1.34 MBytes
BBR:		2.34 Gbits/sec	223 KBytes

For freebsd and RACK functions the CC is cubic.

The last column is Cwnd. BBR's Cwnd looks quite small.

There's also a report on Telegram Taiwan FreeBSD chat group, but without performance details.

I believe there is something wrong with BBR. This is not a reasonable good performance compared with
other tcp congestion control algorithms.

Or am I missing something ?

Best regards,
Zhenlei