Internet problem after recent rewrite of mbuf

[Matthew Dillon]

    I don't think it could be the 29 July commit, but it could
    be one of the later ones.

    If possible I would like you to try the latest kernel again, but
    this time see if the net.inet.tcp.avoid_pure_win_update sysctl 
    makes a difference.  It defaults to 1.  See if setting it to 0 
    solves your problem. 

    If not I will give you a patch to back-out the other tcp related
    windowing change we made and we will see if that has an effect.
    There is a known issue with exponential window expansion potentially
    not working correctly with the current patches

    Another thing that would be very useful would be tcpdump output showing
    the session.  e.g. in one window do this:

    tcpdump -n -i <network_ifc> -l  port 80 > outputfile

    And in another try to load amazon.com (running the kernel that is
    causing the problem.  Then ^C the tcpdump and post the output.

    --

    I tried 'simulating' the issue by using IPFW to create a dummynet
    pipe limited to 1 KByte/s on my test box, and then used elinks to
    connect to amazon.com, but it seemed to work fairly well.  It loaded
    amazon.com in around ~20 seconds.

					-Matt
					Matthew Dillon 
					<dillon at xxxxxxxxxxxxx>



:Hi Matt and others,
:
:After recent kernel update(4 August from 20 July) I noticed 
:that some internet websites take really long time to load
:(connection speed drops to around 50B/s(but is not active)
:with all browsers that I tried, links, elinks, w3m, firefox).
:
:This doesn't happen on all websites (there is a not so
:noticeable slow down on google, but sites such as amazon.com
:become totally unloadable. I was able to load 8.1KiB of
:amazon.com in 9 minutes with elinks!). Connecting to my
:ISP's mail and news servers doesn't seem to be affected.
:
:With the help of Jeffrey Hsu, the source of the problem
:seems to be a commit on 29 July to 
:sys/kern/uicp_mbuf.c and others (I'm not fully sure is it
:that commit, or a commit on 31 July).
:
:After backing out my src/sys to 29 July, and recompiling
:the kernel the problem seems to disappear (amazon.com loads
:in a few seconds with elinks).
:
:I use an old serial modem (Pace Linnet 34 Plus) with a few
:scripts from slackware (IIRC version 9) to connect to my ISP.
:
:TIA.
:
:-- 
:Sarunas Vancevicius