linux-kernel - Re: [PATCH 08/24] net, diet: Make TCP metrics optional

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Message-ID: <20140507043346.GE5619@two.firstfloor.org>
Date:	Wed, 7 May 2014 06:33:46 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Andi Kleen <ak@...ux.intel.com>,
	Richard Cochran <richardcochran@...il.com>,
	josh@...htriplett.org, David Miller <davem@...emloft.net>,
	andi@...stfloor.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, tom.zanussi@...ux.intel.com
Subject: Re: [PATCH 08/24] net, diet: Make TCP metrics optional

On Tue, May 06, 2014 at 04:29:39PM -0700, Eric Dumazet wrote:
> On Tue, 2014-05-06 at 14:05 -0700, Andi Kleen wrote:
> 
> > - Make GRO optional.
> > This is purely a performance feature for high bandwidth.
> 
> Make this properly then, instead of relying on LTO.
> 
> We did preliminary work to put this stuff in separate files, but its not
> complete yet.

FWIW doesn't matter for LTO.

> 
> tcpv4_offload has pointers to tcp4_gro_receive() and tcp4_gro_complete()
> 
> Is LTO smart enough to understand this will never be called, and do
> proper code elimination of whole _gro_ helpers ?

When there are pointers in static objects it cannot eliminate it for C
(it may work for C++)

However if you just  remove the pointer it'll remove the rest.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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