netdev - Re: TSO trimming question

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Message-Id: <20071220.203658.19427671.davem@davemloft.net>
Date:	Thu, 20 Dec 2007 20:36:58 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	jheffner@....edu
Cc:	ilpo.jarvinen@...sinki.fi, netdev@...r.kernel.org,
	herbert@...dor.apana.org.au
Subject: Re: TSO trimming question

From: John Heffner <jheffner@....edu>
Date: Thu, 20 Dec 2007 11:02:21 -0500

> David Miller wrote:
> > From: "Ilpo_Järvinen" <ilpo.jarvinen@...sinki.fi>
> > Date: Thu, 20 Dec 2007 13:40:51 +0200 (EET)
> > 
> >> [PATCH] [TCP]: Fix TSO deferring
> >>
> >> I'd say that most of what tcp_tso_should_defer had in between
> >> there was dead code because of this.
> >>
> >> Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
> > 
> > Yikes!!!!!
> > 
> > John, we've been living a lie for more than a year. :-/
> > 
> > On the bright side this explains a lot of small TSO frames I've been
> > seeing in traces over the past year but never got a chance to
> > investigate.
> 
> Ouch.  This fix may improve some benchmarks.
> 
> Re-checking this function was on my list of things to do because I had 
> also noticed some TSO frames that seemed a bit small.  This clearly 
> explains it.

What I'll do for now is I'll put this into net-2.6.25 to let it
"cook" for a while.  It's an obvious fix but it's enabling code
that's effectively been disabled for more than a year so something
might turn up that we need to fix.
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