Date: Sat, 9 Aug 2014 20:32:12 -0700 From: John-Mark Gurney <jmg@funkthat.com> To: Niu Zhixiong <kaiaixi@gmail.com> Cc: Michael Tuexen <Michael.Tuexen@lurchi.franken.de>, Bill Yuan <bycn82@gmail.com>, freebsd-net@freebsd.org Subject: Re: A problem on TCP in High RTT Environment. Message-ID: <20140810033212.GL83475@funkthat.com> In-Reply-To: <CAOENNMARg36KH1Y%2B0wG8pd7sSf8XKnMf6g790_KiKaj3Mdwyjw@mail.gmail.com> References: <CAOENNMA_CiBDJc0kchzUbTcf_JBwTJPF=PdBAUB6FPo-KzYkeQ@mail.gmail.com> <20140809184232.GF83475@funkthat.com> <8AE1AC56-D52F-4F13-AAA3-BB96042B37DD@lurchi.franken.de> <20140809204500.GG83475@funkthat.com> <3F6BC212-4223-4AAC-8668-A27075DC55C2@lurchi.franken.de> <CAOENNMCPuiYS7LHwMfOczhZ4yisjGkpOmWzv2pcAoi9Hhzb7dw@mail.gmail.com> <20140810022350.GI83475@funkthat.com> <CAOENNMB3=FZx5kSHVPDPBTtMKbmYJ=c_XNMcuYuoLPe=6U%2Bkxg@mail.gmail.com> <CAOENNMARg36KH1Y%2B0wG8pd7sSf8XKnMf6g790_KiKaj3Mdwyjw@mail.gmail.com>
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Niu Zhixiong wrote this message on Sun, Aug 10, 2014 at 10:50 +0800: > I am sorry that I upload a WRONG SCTP capture. But, the throughput is same. > SCTP is double than TCP, about 18Mbps. > ??? > sctp_2.pcapng.gz > <https://docs.google.com/file/d/0By8sTL79ob4tMlh4WDlTSndHX0k/edit?usp=drive_web>; > ??? Ok, the owin graph is very interesting... We do have a full 2MB window on the receiver side, but for some reason, we only ever have just under 6k outstanding on the connection... So, it looks like we send for a short period of time, and then stop sending... Do you have LRO enabled? I think it might be related to: https://svnweb.freebsd.org/changeset/base/r256920 As I'm seeing >100ms gaps where the sender doesn't send any data, and as soon as more than one ack comes in, the next segment goes out... If we only receive a single ack, then we wait for a timeout before sending the next segment.. Can you try to disable LRO on the receiving host? ifconfig <iface> -lro And see if that helps... If it does... Applying the patch, or compiling a more recent kernel from stable/10 that is after r257367 as that is was the date that the change was merged... > On Sun, Aug 10, 2014 at 10:42 AM, Niu Zhixiong <kaiaixi@gmail.com> wrote: > > > I am sure that wnd is about 2MB all the time. > > This is my latest capture, plz see Google Drive. > > In the latest test, TCP(0s-120s) is about 9Mbps and SCTP(0s-120s) is about > > 18Mbps. > > (The bandwidth(20Mbps) and delay(200ms) is set by dummynet) > > The SCTP and TCP are tested in same environment. > > > > ??? > > sctp.pcapng.gz > > <https://docs.google.com/file/d/0By8sTL79ob4tYl9sM2V5a19iNVU/edit?usp=drive_web>; > > ?????? > > tcp.pcapng.gz > > <https://docs.google.com/file/d/0By8sTL79ob4tV0NMR1FYLUQ3MWs/edit?usp=drive_web>; > > ??? > > > > > > > > Regards, > > Niu Zhixiong > > ????????????????????????????????????????????? > > kaiaixi@gmail.com > > > > > > On Sun, Aug 10, 2014 at 10:23 AM, John-Mark Gurney <jmg@funkthat.com> > > wrote: > > > >> Niu Zhixiong wrote this message on Sun, Aug 10, 2014 at 10:12 +0800: > >> > During the TCP4 transmission. > >> > Proto Recv-Q Send-Q Local Address Foreign Address > >> (state) > >> > tcp4 0 2097346 10.0.10.2.13504 10.0.10.3.9000 > >> > ESTABLISHED > >> > >> Ok, so you are getting a full 2MB in there, and w/ that, you should > >> easily be saturating your pipe... > >> > >> The next thing would be to get a tcpdump, and take a look at the > >> window size.. Wireshark has lots of neat tools to make this analysis > >> easy... Another tool that is good is tcptrace.. It can output a > >> variety of different graphs that will help you track down, and see > >> what part of the system is the problem... > >> > >> You probably only need a few tens of seconds of the tcpdump... > >> > >> > On Sun, Aug 10, 2014 at 4:58 AM, Michael Tuexen < > >> > Michael.Tuexen@lurchi.franken.de> wrote: > >> > > >> > > > >> > > On 09 Aug 2014, at 22:45, John-Mark Gurney <jmg@funkthat.com> wrote: > >> > > > >> > > > Michael Tuexen wrote this message on Sat, Aug 09, 2014 at 21:51 > >> +0200: > >> > > >> > >> > > >> On 09 Aug 2014, at 20:42, John-Mark Gurney <jmg@funkthat.com> > >> wrote: > >> > > >> > >> > > >>> Niu Zhixiong wrote this message on Fri, Aug 08, 2014 at 20:34 > >> +0800: > >> > > >>>> Dear all, > >> > > >>>> > >> > > >>>> Last month, I send problems related to FTP/TCP in a high RTT > >> > > environment. > >> > > >>>> After that, I setup a simulation environment(Dummynet) to test > >> TCP > >> > > and SCTP > >> > > >>>> in high delay environment. After finishing the test, I can see > >> TCP is > >> > > >>>> always slower than SCTP. But, I think it is not possible. (Plz > >> see the > >> > > >>>> figure in the attachment). When the delay is 200ms(means > >> RTT=400ms). > >> > > >>>> Besides, the TCP is extremely slow. > >> > > >>>> > >> > > >>>> ALL BW=20Mbps, DELAY= 0 ~ 200MS, Packet LOSS = 0 (by dummynet) > >> > > >>>> > >> > > >>>> This is my parameters: > >> > > >>>> FreeBSD vfreetest0 10.0-RELEASE FreeBSD 10.0-RELEASE #0: Thu Aug > >> 7 > >> > > >>>> 11:04:15 HKT 2014 > >> > > >>>> > >> > > >>>> sysctl net.inet.tcp > >> > > >>> > >> > > >>> [...] > >> > > >>> > >> > > >>>> net.inet.tcp.recvbuf_auto: 0 > >> > > >>> > >> > > >>> [...] > >> > > >>> > >> > > >>>> net.inet.tcp.sendbuf_auto: 0 > >> > > >>> > >> > > >>> Try enabling this... This should allow the buffer to grow large > >> enough > >> > > >>> to deal w/ the higher latency... > >> > > >>> > >> > > >>> Also, make sure your program isn't setting the recv buffer size > >> as that > >> > > >>> will disable the auto growing... > >> > > >> I think the program sets the buffer to 2MB, which it also does for > >> SCTP. > >> > > >> So having both statically at the same size makes sense for the > >> > > comparison. > >> > > >> I remember that there was a bug in the combination of LRO and > >> delayed > >> > > ACK, > >> > > >> which was fixed, but I don't remember it was fixed before 10.0... > >> > > > > >> > > > Sounds like disabling LRO and TSO would be a useful test to see if > >> that > >> > > > improves things... But hiren said that the fix made it, so... > >> > > > > >> > > >>> If you use netstat -a, you should be able to see the send-q on the > >> > > >>> sender grow as necessary... > >> > > > > >> > > > Also, getting the send-q output while it's running would let us know > >> > > > if the buffer is getting to 2MB or not... > >> > > That is correct. Niu: Can you provide this? -- John-Mark Gurney Voice: +1 415 225 5579 "All that I will do, has been done, All that I have, has not."
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