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Re: fix TCP roundtrip time update code

To: davidm@xxxxxxxxxx
Subject: Re: fix TCP roundtrip time update code
From: Nivedita Singhvi <niv@xxxxxxxxxx>
Date: Tue, 03 Jun 2003 23:04:02 -0700
Cc: "David S. Miller" <davem@xxxxxxxxxx>, kuznet@xxxxxxxxxxxxx, jmorris@xxxxxxxxxxxxxxxx, gandalf@xxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, linux-ia64@xxxxxxxxxxxxx, netdev@xxxxxxxxxxx, akpm@xxxxxxxxx
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David Mosberger wrote:

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

Hmm, ditto, except I was way down at --rate 300 (was seeing client
errors of fd-unavail). Have ulimited upwards but am still seeing
them..

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).

You can hike /proc/sys/net/ipv4/tcp_tw_recycle for that.

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

I saw a few AbortOnTimeouts, but no AbortFailed counts.

Those should be TCPAbortOnTimeout counts, rather than TCPAbortFailed
errors, I would expect? Why AbortFailed?  Coming from IP via
tcp_transmit_skb()?

thanks,
Nivedita



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