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Re: Raise initial congestion window size / speedup slow start?

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From: H.K. Jerry Chu
Subject: Re: Raise initial congestion window size / speedup slow start?
Date: Friday, July 16, 2010 - 5:36 pm

On Fri, Jul 16, 2010 at 10:01 AM, Patrick McManus <mcmanus@ducksong.com> wrote:

We have found two issues when altering initcwnd through the ip route cmd:
1. initcwnd is actually capped by sndbuf (i.e., tcp_wmem[1], which is
defaulted to a small value of 16KB). This problem has been made obscured
by the TSO code, which fudges the flow control limit (and could be a bug by
itself).

2. the congestion backoff code is supposed to take inflight, rather than cwnd,
but initcwnd presents a special case. I don't fully understand the code yet to
propose a fix.


This is partly due to our load balancer policy resulting in poor cache hit,
partly due to the sheer volumes of remote clients. Some of colleagues
tried to change the host cache to a /24 subnet cache but the result wasn't
that good either (sorry I don't remember all the details.)


Please voice your support to TCPM then :)

Jerry

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Messages in current thread:
Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 3:43 am)
Re: Raise initial congestion window size / speedup slow start?, Alan Cox, (Wed Jul 14, 4:58 am)
Re: Raise initial congestion window size / speedup slow start?, Bill Davidsen, (Wed Jul 14, 8:21 am)
Re: Raise initial congestion window size / speedup slow start?, David Miller, (Wed Jul 14, 11:15 am)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 11:32 am)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 11:48 am)
Re: Raise initial congestion window size / speedup slow start?, Stephen Hemminger, (Wed Jul 14, 12:10 pm)
Re: Raise initial congestion window size / speedup slow start?, Rick Jones, (Wed Jul 14, 1:17 pm)
Re: Raise initial congestion window size / speedup slow start?, Mitchell Erblich, (Wed Jul 14, 2:47 pm)
Re: Raise initial congestion window size / speedup slow start?, David Miller, (Wed Jul 14, 2:55 pm)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 3:05 pm)
Re: Raise initial congestion window size / speedup slow start?, Hagen Paul Pfeifer, (Wed Jul 14, 3:13 pm)
Re: Raise initial congestion window size / speedup slow start?, Rick Jones, (Wed Jul 14, 3:19 pm)
Re: Raise initial congestion window size / speedup slow start?, Hagen Paul Pfeifer, (Wed Jul 14, 3:36 pm)
Re: Raise initial congestion window size / speedup slow start?, Hagen Paul Pfeifer, (Wed Jul 14, 3:40 pm)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 3:52 pm)
Re: Raise initial congestion window size / speedup slow start?, Hagen Paul Pfeifer, (Wed Jul 14, 4:01 pm)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 4:01 pm)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Wed Jul 14, 4:05 pm)
Re: Raise initial congestion window size / speedup slow start?, Bill Fink, (Wed Jul 14, 7:52 pm)
Re: Raise initial congestion window size / speedup slow start?, Bill Fink, (Wed Jul 14, 8:49 pm)
Re: Raise initial congestion window size / speedup slow start?, Tom Herbert, (Wed Jul 14, 9:12 pm)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Wed Jul 14, 9:51 pm)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Wed Jul 14, 10:09 pm)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Wed Jul 14, 10:29 pm)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Thu Jul 15, 12:48 am)
Re: Raise initial congestion window size / speedup slow start?, Alan Cox, (Thu Jul 15, 3:33 am)
Re: Raise initial congestion window size / speedup slow start?, Bill Davidsen, (Thu Jul 15, 8:10 am)
Re: Raise initial congestion window size / speedup slow start?, Jerry Chu, (Thu Jul 15, 10:36 am)
Re: Raise initial congestion window size / speedup slow start?, Rick Jones, (Thu Jul 15, 12:51 pm)
Re: Raise initial congestion window size / speedup slow start?, Stephen Hemminger, (Thu Jul 15, 1:48 pm)
Re: Raise initial congestion window size / speedup slow start?, Bill Davidsen, (Thu Jul 15, 4:14 pm)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Thu Jul 15, 5:23 pm)
Re: Raise initial congestion window size / speedup slow start?, Henrique de Moraes H ..., (Thu Jul 15, 7:58 pm)
Re: Raise initial congestion window size / speedup slow s ..., Hagen Paul Pfeifer, (Fri Jul 16, 2:03 am)
Re: Raise initial congestion window size / speedup slow start?, Patrick McManus, (Fri Jul 16, 10:01 am)
Re: Raise initial congestion window size / speedup slow start?, Ed W, (Fri Jul 16, 10:41 am)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Fri Jul 16, 5:36 pm)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Fri Jul 16, 6:23 pm)
Re: Raise initial congestion window size / speedup slow start?, Rick Jones, (Mon Jul 19, 10:08 am)
Re: Raise initial congestion window size / speedup slow start?, H.K. Jerry Chu, (Mon Jul 19, 3:51 pm)
Re: Raise initial congestion window size / speedup slow start?, Hagen Paul Pfeifer, (Mon Jul 19, 4:42 pm)