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Date:      Sun, 04 Nov 2012 22:57:40 +0100
From:      Andre Oppermann <andre@freebsd.org>
To:        Andreas Tobler <andreast-list@fgznet.ch>
Cc:        Kim Culhan <kim@kim.net>, Dimitry Andric <dimitry@andric.com>, freebsd-current@freebsd.org, Adrian Chadd <adrian@freebsd.org>
Subject:   Re: weird network problems on current since 10/28/2012
Message-ID:  <5096E4D4.6000000@freebsd.org>
In-Reply-To: <5096CCDE.7090305@fgznet.ch>
References:  <201211031740.qA3HeqVX001622@pozo.com> <CAJ-VmomAR8N8ovhC7La3ttG=7Qu_%2BVwD30tPxFBpzC37eg9CHA@mail.gmail.com> <201211040113.qA41DfLn001577@pozo.com> <50964FBB.4010600@andric.com> <d125c29193960f0932391c161dca233e.squirrel@webmail.kim.net> <50967453.5090503@freebsd.org> <5096CCDE.7090305@fgznet.ch>

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On 04.11.2012 21:15, Andreas Tobler wrote:
> On 04.11.12 14:57, Andre Oppermann wrote:
>> On 04.11.2012 13:11, Kim Culhan wrote:
>>> On Sun, November 4, 2012 6:21 am, Dimitry Andric wrote:
>>>> On 2012-11-04 02:13, Manfred Antar wrote:
>>>>> At 03:29 PM 11/3/2012, Adrian Chadd wrote:
>>>> After the commit, there was a small discussion thread on svn-src-head@
>>>> about the possible problems with the approach.  Maybe you are
>>>> experiencing those?
>>>>
>>>> As the commit message says, you should be able to turn the feature off
>>>> using:
>>>>
>>>>      sysctl net.inet.tcp.experimental.initcwnd10=0
>>>>
>>>> Can you please try that, and see if the problems go away?
>>>
>>> FWIW this did not make the problem go away on 2 machines.
>>
>> Yes, this very much looks like the same problem as in PR/173309.
>>
>> Please try the attached patch.  It fixes the connection hang issue.
>> There may be a second issue I debugging currently base on the feedback
>> from Fabian Keil.
>
> I jump into this thread since I have a similar network issue.
>
> My scenario:
>
> 'make installkernel DESTDIR=/netboot/test' to a nfs mounted drive.
> The nfs drive on the server is an ufs fs. No zfs.
>
> Up to r242261 I can install the kernel (or world) in a fluent way to the
> nfs destination.
>
>>From r242262 it doesn't work smooth. I have stalls, sometimes my
> patience is not enough and I kill the process.
>
> I tried 242266 with the above mentioned patch. No real success.
>
> How can I help/test?

Please try the attach patch instead of the above mentioned one.

-- 
Andre

Index: netinet/tcp_output.c
===================================================================
--- netinet/tcp_output.c        (revision 242577)
+++ netinet/tcp_output.c        (working copy)
@@ -228,7 +228,7 @@
         tso = 0;
         mtu = 0;
         off = tp->snd_nxt - tp->snd_una;
-       sendwin = min(tp->snd_wnd, tp->snd_cwnd);
+       sendwin = ulmax(ulmin(tp->snd_wnd - off, tp->snd_cwnd), 0);

         flags = tcp_outflags[tp->t_state];
         /*
@@ -249,7 +249,7 @@
             (p = tcp_sack_output(tp, &sack_bytes_rxmt))) {
                 long cwin;

-               cwin = min(tp->snd_wnd, tp->snd_cwnd) - sack_bytes_rxmt;
+               cwin = ulmin(tp->snd_wnd - off, tp->snd_cwnd) - sack_bytes_rxmt;
                 if (cwin < 0)
                         cwin = 0;
                 /* Do not retransmit SACK segments beyond snd_recover */
@@ -355,7 +355,7 @@
                          * sending new data, having retransmitted all the
                          * data possible in the scoreboard.
                          */
-                       len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd)
+                       len = ((long)ulmin(so->so_snd.sb_cc, tp->snd_wnd - off)
                                - off);
                         /*
                          * Don't remove this (len > 0) check !



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