> On Oct 22, 2022, at 2:16 AM, Michael Tuexen <michael.tue...@lurchi.franken.de > <mailto:michael.tue...@lurchi.franken.de>> wrote: > >> On 21. Oct 2022, at 17:00, Zhenlei Huang <zlei.hu...@gmail.com >> <mailto:zlei.hu...@gmail.com>> wrote: >> >> >>> On Oct 21, 2022, at 10:34 PM, Michael Tuexen >>> <michael.tue...@lurchi.franken.de >>> <mailto:michael.tue...@lurchi.franken.de>> wrote: >>> >>>> On 21. Oct 2022, at 16:19, Zhenlei Huang <zlei.hu...@gmail.com >>>> <mailto:zlei.hu...@gmail.com>> wrote: >>>> >>>> Hi, >>>> >>>> While I was repeating >>>> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258755 >>>> <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258755>, I observed a >>>> strange behavior. The TCP ACKs from FreeBSD host are too aggressive. >>>> >>>> My setup is simple: >>>> A B >>>> [ MacOS ] <====> [ FreeBSD VM ] >>>> 192.168.120.1 192.168.12.134 (disable tso and lro) >>>> While A <--- B, i.e. A as server and B as client, the packets rate looks >>>> good. >>>> >>>> One session on B: >>>> >>>> root@:~ # iperf3 -c 192.168.120.1 -b 10m >>>> Connecting to host 192.168.120.1, port 5201 >>>> [ 5] local 192.168.120.134 port 54459 connected to 192.168.120.1 port 5201 >>>> [ ID] Interval Transfer Bitrate Retr Cwnd >>>> [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes >>>> >>>> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes >>>> >>>> - - - - - - - - - - - - - - - - - - - - - - - - - >>>> [ ID] Interval Transfer Bitrate Retr >>>> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec 0 >>>> sender >>>> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec >>>> receiver >>>> >>>> iperf Done. >>>> >>>> Another session on B: >>>> >>>> root@:~ # netstat -w 1 -I vmx0 >>>> input vmx0 output >>>> packets errs idrops bytes packets errs bytes colls >>>> 0 0 0 0 0 0 0 0 >>>> 0 0 0 0 0 0 0 0 >>>> 342 0 0 22600 526 0 775724 0 >>>> 150 0 0 9900 851 0 1281454 0 >>>> 109 0 0 7194 901 0 1357850 0 >>>> 126 0 0 8316 828 0 1246632 0 >>>> 122 0 0 8052 910 0 1370780 0 >>>> 109 0 0 7194 819 0 1233702 0 >>>> 120 0 0 7920 910 0 1370780 0 >>>> 110 0 0 7260 819 0 1233702 0 >>>> 123 0 0 8118 910 0 1370780 0 >>>> 109 0 0 7194 819 0 1233702 0 >>>> 73 0 0 5088 465 0 686342 0 >>>> 0 0 0 0 0 0 0 0 >>>> 0 0 0 0 0 0 0 0 >>>> >>>> >>>> >>>> ================================================================ >>>> >>>> >>>> While A ---> B, i.e. A as client and B as server, the ACKs sent from B >>>> looks strange. >>>> >>>> Session on A: >>>> >>>> % iperf3 -c 192.168.120.134 -b 10m >>>> Connecting to host 192.168.120.134, port 5201 >>>> [ 5] local 192.168.120.1 port 52370 connected to 192.168.120.134 port 5201 >>>> [ ID] Interval Transfer Bitrate >>>> [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec >>>> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec >>>> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec >>>> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec >>>> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec >>>> - - - - - - - - - - - - - - - - - - - - - - - - - >>>> [ ID] Interval Transfer Bitrate >>>> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec >>>> sender >>>> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec >>>> receiver >>>> >>>> iperf Done. >>>> >>>> Session on B: >>>> >>>> root@:~ # netstat -w 1 -I vmx0 >>>> input vmx0 output >>>> packets errs idrops bytes packets errs bytes colls >>>> 0 0 0 0 0 0 0 0 >>>> 0 0 0 0 0 0 0 0 >>>> 649 0 0 960562 330 0 21800 0 >>>> 819 0 0 1233702 415 0 27390 0 >>>> 910 0 0 1370780 459 0 30294 0 >>>> 819 0 0 1233702 415 0 27390 0 >>>> 910 0 0 1370780 459 0 30294 0 >>>> 910 0 0 1370780 460 0 30360 0 >>>> 819 0 0 1233702 414 0 27324 0 >>>> 910 0 0 1370780 460 0 30360 0 >>>> 819 0 0 1233702 414 0 27324 0 >>>> 910 0 0 1370780 460 0 30360 0 >>>> 285 0 0 412287 147 0 9981 0 >>>> 0 0 0 0 0 0 0 0 >>>> 0 0 0 0 0 0 0 0 >>>> 0 0 0 0 0 0 0 0 >>>> >>>> >>>> The ACK packets replied from B (the FreeBSD VM) are too aggressive. They >>>> are >>>> about one half of TCP packets received from A. >>>> >>>> I've tested with different bitrates, from 10m to 300m, all behave the same. >>>> Tested with baremetal FreeBSD 13.1 Box as B (with intel em driver), the >>>> bitrates is 1g, also behaves the same. >>>> >>>> Also tried different FreeBSD versions, 11.4, 12.3, stable/13 and >>>> current/14 all >>>> behave the same. >>>> >>>> >>>> My question is, is that the expected behavior of current default TCP stack? >>> That is what I would expect. TCP (on FreeBSD) is acking every other packet. >>> This >>> is also what is specified. MacOS, at least newer versions, send less ACKs. >> Thanks for fast response! >> >> My have old memories about SACK which helps TCP performance. This behavior >> seems odd from my mind. But those memories date back to 2008, that is 14 >> years ago. > I don't think anything has changed since then from a specification point of > view Hacked some RFCs from 1122, and the transport protocol is stable, and apparently it should be. >> >> The current implementation of TCP stack in FreeBSD head is too complexed for >> me. >> Can you please point me the RFCs specifying this? So I can start over with a >> quick glue. > Send an ACK for every other frame if everything is OK, send it immediately if > there are some gaps: > https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3 > <https://datatracker.ietf.org/doc/html/rfc9293#section-3.8.6.3> > This applies also to the case where you use SACK. I think I confused SACK with delayed ACK.
Thanks! > > Best regards > Michael >> >> Thanks! >>> >>> Best regards >>> Michael >>>> >>>> >>>> >>>> Best regards, >>>> Zhenlei
