netdev - Re: Increasing TCP initial cwnd

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Date:	Mon, 26 Oct 2009 15:57:44 +0200 (EET)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Yair Gottdenker <yairgott@...il.com>
cc:	Netdev <netdev@...r.kernel.org>
Subject: Re: Increasing TCP initial cwnd

On Mon, 26 Oct 2009, Ilpo Järvinen wrote:

> On Mon, 26 Oct 2009, Yair Gottdenker wrote:
> 
> > I am working on research project to control the sender initial
> > congestion window size. I am trying to allow user space to set the
> > initial congestion window size but with no luck. The sender always
> > sends just 4 packets disregarding from the snd_cwnd.
> > 
> > I am working on kernel version 2.6.31.3.
> > 
> > I made the following changes:
> > 1. tcp_ipv4.c -> in function tcp_v4_init_sock, changed from
> > tp->snd_cwnd = 2 to tp->snd_cwnd = user_space_initial_cwnd.
> > 2. tcp_output.c -> tcp_init_cwnd - to always return user_space_initial_cwnd.
> > 3. tcp_cong.c -> tcp_slow_start- to always return user_space_initial_cwnd.
> > 
> > Any help will be more than welcome.
> 
> How about trying tcp_init_metrics in tcp_input.c?

Also, now that I looked. I don't understand what interesting you find in 
tcp_slow_start to modify? That certainly has nothing to do with initial 
window. ....Then you also might want to play with RW but that 
is out-of-scope of your question, just mentioning it for completeleness.

-- 
 i.