Date: Fri, 21 Oct 2022 16:34:04 +0200 From: Michael Tuexen <michael.tuexen@lurchi.franken.de> To: Zhenlei Huang <zlei.huang@gmail.com> Cc: freebsd-net@freebsd.org Subject: Re: Too aggressive TCP ACKs Message-ID: <712641B3-5196-40CC-9B64-04637F16F649@lurchi.franken.de> In-Reply-To: <75D35F36-7759-4168-ADBA-C2414F5B53BC@gmail.com> References: <75D35F36-7759-4168-ADBA-C2414F5B53BC@gmail.com>
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> On 21. Oct 2022, at 16:19, Zhenlei Huang <zlei.huang@gmail.com> wrote: >=20 > Hi, >=20 > While I was repeating = https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D258755, I observed a > strange behavior. The TCP ACKs from FreeBSD host are too aggressive. >=20 > My setup is simple: > A B > [ MacOS ] <=3D=3D=3D=3D> [ 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. >=20 > One session on B: >=20 > 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 =20 > [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 > [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 > [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 > [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 > [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 > [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 > [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 > [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 = KBytes =20 > [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 = KBytes =20 > - - - - - - - - - - - - - - - - - - - - - - - - - > [ 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 >=20 > iperf Done. >=20 > Another session on B: >=20 > 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 >=20 >=20 >=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D >=20 >=20 > While A ---> B, i.e. A as client and B as server, the ACKs sent from B = looks strange. >=20 > Session on A: >=20 > % 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 =20= > [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec =20= > [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec =20= > [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec =20= > [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec =20= > [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec =20= > [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec =20= > [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec =20= > [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec =20= > [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec =20= > - - - - - - - - - - - - - - - - - - - - - - - - - > [ 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 >=20 > iperf Done. >=20 > Session on B: >=20 > 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 >=20 >=20 > The ACK packets replied from B (the FreeBSD VM) are too aggressive. = They are > about one half of TCP packets received from A. >=20 > 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=20 > bitrates is 1g, also behaves the same. >=20 > Also tried different FreeBSD versions, 11.4, 12.3, stable/13 and = current/14 all=20 > behave the same. >=20 >=20 > 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. Best regards Michael >=20 >=20 >=20 > Best regards, > Zhenlei >=20
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