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Re: fix TCP roundtrip time update code

To: "David S. Miller" <davem@xxxxxxxxxx>
Subject: Re: fix TCP roundtrip time update code
From: David Mosberger <davidm@xxxxxxxxxxxxxxxxx>
Date: Tue, 3 Jun 2003 21:35:55 -0700
Cc: niv@xxxxxxxxxx, kuznet@xxxxxxxxxxxxx, jmorris@xxxxxxxxxxxxxxxx, davidm@xxxxxxxxxx, gandalf@xxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxx, netdev@xxxxxxxxxxx, akpm@xxxxxxxxx
In-reply-to: <20030603.202320.59680883.davem@redhat.com>
References: <200306040043.EAA24505@dub.inr.ac.ru> <3EDD52F5.8090706@us.ibm.com> <20030603.202320.59680883.davem@redhat.com>
Reply-to: davidm@xxxxxxxxxx
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>>>>> On Tue, 03 Jun 2003 20:23:20 -0700 (PDT), "David S. Miller" 
>>>>> <davem@xxxxxxxxxx> said:

  DaveM>    From: Nivedita Singhvi <niv@xxxxxxxxxx> Date: Tue, 03 Jun
  DaveM> 2003 19:01:25 -0700
  DaveM>    But, FYI, DaveM and Alexey, we tried reproducing the
  DaveM> stalls we (Dave Hansen, Troy Wilson) had seen during
  DaveM> SpecWeb99 runs and couldn't reproduce them on 2.5.69. (Same
  DaveM> config, etc). So its possible our hang/stalls were some other
  DaveM> issue that got silently fixed (or more likely, possibly the
  DaveM> same thing but other changes minimized us running into the
  DaveM> problem).

  DaveM> I think this means nothing, and that you can infer nothing
  DaveM> from such results.

  DaveM> My understanding is that the problem case triggers only when
  DaveM> a timeout based retransmit occurs.  On LAN this tends to be
  DaveM> extremely rare.  Although under enough traffic load it can
  DaveM> occur.

  DaveM> So if your old SpecWEB99 lab tended more to trigger timeout
  DaveM> based retransmits on LAN, and your new test network does not,
  DaveM> then your new test network will tend to not reproduce the bug
  DaveM> regardless of whether the bug is present in the kernel or not
  DaveM> :-)

Is this where I get to plug httperf?  It triggered the bug reliably in
less than 10 secs. ;-)

        --david

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