netdev - Re: A Linux TCP SACK Question

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Date:	Wed, 16 Apr 2008 02:35:51 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ilpo.jarvinen@...sinki.fi
Cc:	johnwheffner@...il.com, wenji@...l.gov, netdev@...r.kernel.org
Subject: Re: A Linux TCP SACK Question

From: "Ilpo_Järvinen" <ilpo.jarvinen@...sinki.fi>
Date: Wed, 16 Apr 2008 12:21:38 +0300 (EEST)

> On Wed, 16 Apr 2008, David Miller wrote:
> 
> > From: "John Heffner" <johnwheffner@...il.com>
> > Date: Tue, 15 Apr 2008 15:40:05 -0700
> > 
> > > Subject: [PATCH] Increase the max_burst threshold from 3 to tp->reordering.
 ...
> > Any objections to my adding this to net-2.6.26?
> 
> I don't have objections.
> 
> But I want to note that tp->reordering does not consider the situation on 
> that specific ACK because its value might originate a number of segments 
> and even RTTs back. I think it could be possible to find a more 
> appropriate value for max_burst locally to an ACK. ...Though it might be a 
> bit over-engineered solution. For SACK we calculate similar metric anyway 
> in tcp_clean_rtx_queue to find if tp->reordering needs to be updated at 
> cumulative ACK and for NewReno min(tp->sacked_out, tp->reordering) + 3
> could perhaps be used (I'm not sure if these would be foolproof in 
> recovery though).

Right, we can tweak this thing further later.

*beep* *beep*

I've added John's patch to net-2.6.26

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