Date: Fri, 21 Oct 2022 15:02:59 +0000 From: "Cui, Cheng" <Cheng.Cui@netapp.com> To: Zhenlei Huang <zlei.huang@gmail.com>, Michael Tuexen <michael.tuexen@lurchi.franken.de> Cc: "freebsd-net@freebsd.org" <freebsd-net@freebsd.org> Subject: Re: Too aggressive TCP ACKs Message-ID: <MN2PR06MB6237E90881035621441597989D2D9@MN2PR06MB6237.namprd06.prod.outlook.com> In-Reply-To: <62A0DD30-B3ED-48BE-9C01-146487599092@gmail.com> References: <75D35F36-7759-4168-ADBA-C2414F5B53BC@gmail.com> <712641B3-5196-40CC-9B64-04637F16F649@lurchi.franken.de> <62A0DD30-B3ED-48BE-9C01-146487599092@gmail.com>
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[-- Attachment #1 --] You can also think about MacOS’s delayed ACK setup in default is conservative. https://developer.apple.com/forums/thread/716394 -- Cheng Cui From: owner-freebsd-net@freebsd.org <owner-freebsd-net@freebsd.org> on behalf of Zhenlei Huang <zlei.huang@gmail.com> Date: Friday, October 21, 2022 at 11:01 AM To: Michael Tuexen <michael.tuexen@lurchi.franken.de> Cc: freebsd-net@freebsd.org <freebsd-net@freebsd.org> Subject: Re: Too aggressive TCP ACKs NetApp Security WARNING: This is an external email. Do not click links or open attachments unless you recognize the sender and know the content is safe. On Oct 21, 2022, at 10:34 PM, Michael Tuexen <michael.tuexen@lurchi.franken.de<mailto:michael.tuexen@lurchi.franken.de>> wrote: On 21. Oct 2022, at 16:19, Zhenlei Huang <zlei.huang@gmail.com<mailto:zlei.huang@gmail.com>> wrote: Hi, While I was repeating 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. 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. Thanks! Best regards Michael Best regards, Zhenlei [-- Attachment #2 --] <html xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40">; <head> <meta http-equiv="Content-Type" content="text/html; charset=Windows-1252"> <meta name="Generator" content="Microsoft Word 15 (filtered medium)"> <style><!-- /* Font Definitions */ @font-face {font-family:Helvetica; panose-1:0 0 0 0 0 0 0 0 0 0;} @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4;} @font-face {font-family:DengXian; panose-1:2 1 6 0 3 1 1 1 1 1;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4;} @font-face {font-family:"\@DengXian"; panose-1:2 1 6 0 3 1 1 1 1 1;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; font-size:10.0pt; font-family:"Calibri",sans-serif;} a:link, span.MsoHyperlink {mso-style-priority:99; color:blue; text-decoration:underline;} span.apple-converted-space {mso-style-name:apple-converted-space;} span.EmailStyle19 {mso-style-type:personal-reply; font-family:"Calibri",sans-serif; color:windowtext;} .MsoChpDefault {mso-style-type:export-only; font-size:10.0pt;} @page WordSection1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in;} div.WordSection1 {page:WordSection1;} --></style> </head> <body lang="EN-US" link="blue" vlink="purple" style="word-wrap:break-word;-webkit-nbsp-mode: space;line-break:after-white-space"> <div class="WordSection1"> <p class="MsoNormal"><span style="font-size:11.0pt">You can also think about MacOS’s delayed ACK setup in default is conservative.<o:p></o:p></span></p> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> <p class="MsoNormal"><span style="font-size:11.0pt"><a href="https://developer.apple.com/forums/thread/716394">https://developer.apple.com/forums/thread/716394</a><o:p></o:p></span></p>; <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> <div> <div> <div> <p class="MsoNormal"><span style="font-size:11.0pt">-- <o:p></o:p></span></p> </div> </div> </div> <p class="MsoNormal"><span style="font-size:11.0pt">Cheng Cui</span><span style="font-size:11.0pt"><o:p></o:p></span></p> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> <div style="border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in"> <p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="font-size:12.0pt;color:black">From: </span></b><span style="font-size:12.0pt;color:black">owner-freebsd-net@freebsd.org <owner-freebsd-net@freebsd.org> on behalf of Zhenlei Huang <zlei.huang@gmail.com><br> <b>Date: </b>Friday, October 21, 2022 at 11:01 AM<br> <b>To: </b>Michael Tuexen <michael.tuexen@lurchi.franken.de><br> <b>Cc: </b>freebsd-net@freebsd.org <freebsd-net@freebsd.org><br> <b>Subject: </b>Re: Too aggressive TCP ACKs<o:p></o:p></span></p> </div> <table class="MsoNormalTable" border="1" cellspacing="0" cellpadding="0" align="left" width="200" style="width:150.0pt;background:#0067C5"> <tbody> <tr> <td nowrap="" style="padding:7.5pt 7.5pt 7.5pt 7.5pt"> <p class="MsoNormal" style="mso-element:frame;mso-element-frame-hspace:2.25pt;mso-element-wrap:around;mso-element-anchor-vertical:paragraph;mso-element-anchor-horizontal:column;mso-height-rule:exactly"> <b><span style="font-family:"Arial",sans-serif;color:yellow">NetApp Security WARNING</span></b><span style="font-family:"Arial",sans-serif;color:yellow">: This is an external email. Do not click links or open attachments unless you recognize the sender and know the content is safe. </span><span style="font-size:11.0pt"><o:p></o:p></span></p> </td> </tr> </tbody> </table> <p class="MsoNormal" style="margin-bottom:12.0pt"><span style="font-size:11.0pt"><br> <br> <o:p></o:p></span></p> <div> <div> <div> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> </div> <div> <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"> <div> <p class="MsoNormal"><span style="font-size:11.0pt">On Oct 21, 2022, at 10:34 PM, Michael Tuexen <<a href="mailto:michael.tuexen@lurchi.franken.de">michael.tuexen@lurchi.franken.de</a>> wrote:<o:p></o:p></span></p> </div> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> <div> <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt;font-variant-caps: normal;orphans: auto;text-align:start;widows: auto;-webkit-text-size-adjust: auto;-webkit-text-stroke-width: 0px;word-spacing:0px"> <p class="MsoNormal"><span style="font-size:9.0pt;font-family:Helvetica">On 21. Oct 2022, at 16:19, Zhenlei Huang <<a href="mailto:zlei.huang@gmail.com">zlei.huang@gmail.com</a>> wrote:<br> <br> Hi,<br> <br> While I was repeating <a href="https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258755">; https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258755</a>, I observed a<br> strange behavior. The TCP ACKs from FreeBSD host are too aggressive.<br> <br> My setup is simple:<br> A B<br> [ MacOS ] <====> [ FreeBSD VM ]<br> 192.168.120.1 192.168.12.134 (disable tso and lro)<br> While A <--- B, i.e. A as server and B as client, the packets rate looks good.<br> <br> One session on B:<br> <br> root@:~ # iperf3 -c 192.168.120.1 -b 10m<br> Connecting to host 192.168.120.1, port 5201<br> [ 5] local 192.168.120.134 port 54459 connected to 192.168.120.1 port 5201<br> [ ID] Interval Transfer Bitrate Retr Cwnd<br> [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes <br> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes <br> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes <br> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec 0 257 KBytes <br> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec 0 257 KBytes <br> - - - - - - - - - - - - - - - - - - - - - - - - -<br> [ ID] Interval Transfer Bitrate Retr<br> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec 0 sender<br> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec receiver<br> <br> iperf Done.<br> <br> Another session on B:<br> <br> root@:~ # netstat -w 1 -I vmx0<br> input vmx0 output<br> packets errs idrops bytes packets errs bytes colls<br> 0 0 0 0 0 0 0 0<br> 0 0 0 0 0 0 0 0<br> 342 0 0 22600 526 0 775724 0<br> 150 0 0 9900 851 0 1281454 0<br> 109 0 0 7194 901 0 1357850 0<br> 126 0 0 8316 828 0 1246632 0<br> 122 0 0 8052 910 0 1370780 0<br> 109 0 0 7194 819 0 1233702 0<br> 120 0 0 7920 910 0 1370780 0<br> 110 0 0 7260 819 0 1233702 0<br> 123 0 0 8118 910 0 1370780 0<br> 109 0 0 7194 819 0 1233702 0<br> 73 0 0 5088 465 0 686342 0<br> 0 0 0 0 0 0 0 0<br> 0 0 0 0 0 0 0 0<br> <br> <br> <br> ================================================================<br> <br> <br> While A ---> B, i.e. A as client and B as server, the ACKs sent from B looks strange.<br> <br> Session on A:<br> <br> % iperf3 -c 192.168.120.134 -b 10m<br> Connecting to host 192.168.120.134, port 5201<br> [ 5] local 192.168.120.1 port 52370 connected to 192.168.120.134 port 5201<br> [ ID] Interval Transfer Bitrate<br> [ 5] 0.00-1.00 sec 1.25 MBytes 10.5 Mbits/sec <br> [ 5] 1.00-2.00 sec 1.25 MBytes 10.5 Mbits/sec <br> [ 5] 2.00-3.00 sec 1.12 MBytes 9.44 Mbits/sec <br> [ 5] 3.00-4.00 sec 1.25 MBytes 10.5 Mbits/sec <br> [ 5] 4.00-5.00 sec 1.12 MBytes 9.44 Mbits/sec <br> [ 5] 5.00-6.00 sec 1.25 MBytes 10.5 Mbits/sec <br> [ 5] 6.00-7.00 sec 1.12 MBytes 9.44 Mbits/sec <br> [ 5] 7.00-8.00 sec 1.25 MBytes 10.5 Mbits/sec <br> [ 5] 8.00-9.00 sec 1.12 MBytes 9.44 Mbits/sec <br> [ 5] 9.00-10.00 sec 1.25 MBytes 10.5 Mbits/sec <br> - - - - - - - - - - - - - - - - - - - - - - - - -<br> [ ID] Interval Transfer Bitrate<br> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec sender<br> [ 5] 0.00-10.00 sec 12.0 MBytes 10.1 Mbits/sec receiver<br> <br> iperf Done.<br> <br> Session on B:<br> <br> root@:~ # netstat -w 1 -I vmx0<br> input vmx0 output<br> packets errs idrops bytes packets errs bytes colls<br> 0 0 0 0 0 0 0 0<br> 0 0 0 0 0 0 0 0<br> 649 0 0 960562 330 0 21800 0<br> 819 0 0 1233702 415 0 27390 0<br> 910 0 0 1370780 459 0 30294 0<br> 819 0 0 1233702 415 0 27390 0<br> 910 0 0 1370780 459 0 30294 0<br> 910 0 0 1370780 460 0 30360 0<br> 819 0 0 1233702 414 0 27324 0<br> 910 0 0 1370780 460 0 30360 0<br> 819 0 0 1233702 414 0 27324 0<br> 910 0 0 1370780 460 0 30360 0<br> 285 0 0 412287 147 0 9981 0<br> 0 0 0 0 0 0 0 0<br> 0 0 0 0 0 0 0 0<br> 0 0 0 0 0 0 0 0<br> <br> <br> The ACK packets replied from B (the FreeBSD VM) are too aggressive. They are<br> about one half of TCP packets received from A.<br> <br> I've tested with different bitrates, from 10m to 300m, all behave the same.<br> Tested with baremetal FreeBSD 13.1 Box as B (with intel em driver), the<span class="apple-converted-space"> </span><br> bitrates is 1g, also behaves the same.<br> <br> Also tried different FreeBSD versions, 11.4, 12.3, stable/13 and current/14 all<span class="apple-converted-space"> </span><br> behave the same.<br> <br> <br> My question is, is that the expected behavior of current default TCP stack?<o:p></o:p></span></p> </blockquote> <p class="MsoNormal"><span style="font-size:9.0pt;font-family:Helvetica">That is what I would expect. TCP (on FreeBSD) is acking every other packet. This<br> is also what is specified. MacOS, at least newer versions, send less ACKs.</span><span style="font-size:11.0pt"><o:p></o:p></span></p> </div> </blockquote> <div> <p class="MsoNormal"><span style="font-size:11.0pt">Thanks for fast response!<o:p></o:p></span></p> </div> <p class="MsoNormal"><span style="font-size:11.0pt"><br> My have old memories about SACK which helps TCP performance. This behavior<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt">seems odd from my mind. But those <span style="color:black">memories date back to 2008, that is 14 years ago.</span><o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt">The current implementation of TCP stack in FreeBSD head is too complexed for me.<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt">Can you please point me the RFCs specifying this? So I can start over with a quick glue.<o:p></o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> <div> <p class="MsoNormal"><span style="font-size:11.0pt">Thanks!<br> <br> <o:p></o:p></span></p> <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"> <div> <p class="MsoNormal"><span style="font-size:9.0pt;font-family:Helvetica"><br> Best regards<br> Michael<br style="caret-color: rgb(0, 0, 0);font-variant-caps: normal;text-align:start;-webkit-text-stroke-width: 0px;word-spacing:0px"> <br> </span><span style="font-size:11.0pt"><o:p></o:p></span></p> <blockquote style="margin-top:5.0pt;margin-bottom:5.0pt"> <p class="MsoNormal"><span style="font-size:9.0pt;font-family:Helvetica"><br> <br> <br> Best regards,<br> Zhenlei<o:p></o:p></span></p> </blockquote> </div> </blockquote> </div> <p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p> </div> </div> </body> </html>
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