netdev - Re: tbench wrt. loopback TSO

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Date:	Mon, 27 Oct 2008 17:19:17 +0200 (EET)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Evgeniy Polyakov <zbr@...emap.net>
cc:	David Miller <davem@...emloft.net>,
	Netdev <netdev@...r.kernel.org>, efault@....de, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: tbench wrt. loopback TSO

On Mon, 27 Oct 2008, Evgeniy Polyakov wrote:

> On Mon, Oct 27, 2008 at 09:49:21AM +0200, Ilpo Järvinen (ilpo.jarvinen@...sinki.fi) wrote:
> > > > That's what I got with the current tree for 8 threads on a 4-way 32-bit
> > > > Xeons (2 physical CPUs) and 8gb of ram:
> > > > gso/tso off: 361.367
> > > > tso/gso on:  354.635
> > > 
> > > Yes, it might do this, in which case tcp_tso_should_defer() simply needs
> > > some tweaking.
> > 
> > Good point, could you Evgeniy verify first if simple goto send_now; in 
> > beginning there recovers it all...
> 
> With direct goto at the begining of the tcp_tso_should_defer()
> and 4403b406 commit git tree (was current yesterday night)
> I got following numbers: 
> 
> with goto:
> tso/gso  on: 358.976, 357.699
> tso/gso off: 368.016, 367.079
> 
> no goto
> tso/gso  on: 353.656, 354.791
> tso/gso off: 364.8, 365.85
> 
> So tcp_tso_should_defer() adds additional problems not counted in
> tso/gso changes.

Noticed that tcp_current_mss does modulo with tso and that it is 
being called from a non-trivial number of places, though ovbiously only 
part of them should be relevant here. ...I'm not sure if that can show 
up though.

-- 
 i.