Re: fix TCP roundtrip time update code

[David Mosberger <davidm@napali.hpl.hp.com>]

>>>>> On Tue, 03 Jun 2003 21:40:18 -0700, Nivedita Singhvi <niv@us.ibm.com> said:

  Nivedita> David Mosberger wrote:
  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. ;-)

  Nivedita> Tarnation!! Ran httperf! Didnt hit it! :(. What were your
  Nivedita> settings?

I used:

 $ httperf --rate 1000 --num-conns 1000000 --verbose --hog --server HOST \
	--uri pathto30KBfile

on 3 clients (for a total of 3000 conns/sec).  You can't go higher
than 1000 conn/sec per client (IP address) because otherwise you run
out of port space (due to TIME_WAIT).

This load worked well for a machine with a single GigE card.  All
network tunables were on the default setting (in particular, the tx
queue len was 300, which is were the losses came from).

With this load, I saw bad RTT values in the route cache within a
couple of seconds after starting the third httperf generator.  It then
took a bit longer (on the order of 1-2 minutes) until the first
TCPAbortFailed errors started to pop up.

	--david