netdev - Re: [PATCH 0/9 Rev3] Implement batching skb API and support in IPoIB

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Message-ID: <20070823203425.2a32fb3f@freepuppy.rosehill.hemminger.net>
Date:	Thu, 23 Aug 2007 20:34:25 -0700
From:	Stephen Hemminger <shemminger@...ux-foundation.org>
To:	hadi@...erus.ca
Cc:	David Miller <davem@...emloft.net>, rick.jones2@...com,
	krkumar2@...ibm.com, gaagaan@...il.com,
	general@...ts.openfabrics.org, herbert@...dor.apana.org.au,
	jagana@...ibm.com, jeff@...zik.org, johnpol@....mipt.ru,
	kaber@...sh.net, mcarlson@...adcom.com, mchan@...adcom.com,
	netdev@...r.kernel.org, peter.p.waskiewicz.jr@...el.com,
	rdreier@...co.com, Robert.Olsson@...a.slu.se, sri@...ibm.com,
	tgraf@...g.ch, xma@...ibm.com
Subject: Re: [PATCH 0/9 Rev3] Implement batching skb API and support in
 IPoIB

On Thu, 23 Aug 2007 18:38:22 -0400
jamal <hadi@...erus.ca> wrote:

> On Thu, 2007-23-08 at 15:30 -0700, David Miller wrote:
> > From: jamal <hadi@...erus.ca>
> > Date: Thu, 23 Aug 2007 18:04:10 -0400
> > 
> > > Possibly a bug - but you really should turn off TSO if you are doing
> > > huge interactive transactions (which is fair because there is a clear
> > > demarcation).
> > 
> > I don't see how this can matter.
> > 
> > TSO only ever does anything if you accumulate more than one MSS
> > worth of data.
> 
> I stand corrected then.
> 
> cheers,
> jamal
> 

For most normal Internet TCP connections, you will see only 2 or 3 packets per TSO
because of ACK clocking. If you turn off delayed ACK on the receiver it
will be even less.

A current hot topic of research is reducing the number of ACK's to make TCP
work better over asymmetric links like 3G.

-- 
Stephen Hemminger <shemminger@...ux-foundation.org>
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