netdev - Re: [PATCH 3/3] net: TCP thin dupack

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Date:	Thu, 29 Oct 2009 16:23:53 +0100
From:	apetlund@...ula.no
To:	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
Cc:	"Andreas Petlund" <apetlund@...ula.no>,
	"Netdev" <netdev@...r.kernel.org>,
	"LKML" <linux-kernel@...r.kernel.org>, shemminger@...tta.com,
	"David Miller" <davem@...emloft.net>
Subject: Re: [PATCH 3/3] net: TCP thin dupack

I apologise that some of you received this mail more than once. My email
client played a HTML-trick on me.

>> +	/* If a thin stream is detected, retransmit after first
>> +	 * received dupack */
>> +	if ((tp->thin_dupack || sysctl_tcp_force_thin_dupack) &&
>> +	    tcp_dupack_heurestics(tp) > 1 && tcp_stream_is_thin(tp))
>> +		return 1;
>> +
>>  	return 0;
>>  }
>
> Have you tested it? ...I doubt this will work like you say and
retransmit
> something when the window is small. ...Besides, you should have built
this
> patch on top of the function rename you submitted earlier as after DaveM
applied that this will no longer even compile...
>
> --
>  i.
>

We have performed extensive tests mapping the effect of the patch you
commented on some months ago. Since then, the only change was the one you
requested of switching tcp_fackets_out() with tcp_dupack_heurestics().
After inspecting the code, I believed the effect should be equal to the
previous, only making considerations for SACK and FACK availability.
Please tell if this will break the intended effect, and I will modify the
patch accordingly.

Graphs from our tests of the original patch can be found at the location
linked to below.  I have tested the new one for functionality, but have
not et performed tests on this scope as the changes were minor. I will, of
course, fix the function rename in the next iteration. Sorry for that.

http://folk.uio.no/apetlund/lktmp/

-AP

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