linux-kernel - Re: [PATCH 4/9] powerpc: inline ip_fast

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Date:	Mon, 29 Feb 2016 08:25:59 +0100
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Denis Kirjanov <kda@...ux-powerpc.org>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>, scottwood@...escale.com,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 4/9] powerpc: inline ip_fast_csum()



Le 23/09/2015 07:43, Denis Kirjanov a écrit :
> On 9/22/15, Christophe Leroy <christophe.leroy@....fr> wrote:
>> In several architectures, ip_fast_csum() is inlined
>> There are functions like ip_send_check() which do nothing
>> much more than calling ip_fast_csum().
>> Inlining ip_fast_csum() allows the compiler to optimise better
> Hi Christophe,
> I did try it and see no difference on ppc64. Did you test with socklib
> with modified loopback and if so do you have any numbers?

Hi Denis,

I put a mftbl at start and end of ip_send_check() and tested on a MPC885:
* Without ip_fast_csum() inlined, approxymatly 7 TB ticks are spent in 
ip_send_check()
* With ip_fast_csum() inlined, approxymatly 5,4 TB ticks are spent in 
ip_send_check()

So it is about 23% time reduction.

Christophe