netdev - Re: [PATCH v3] powerpc: Implement csum_ipv6

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Message-ID: <20180524195538.GE17342@gate.crashing.org>
Date:   Thu, 24 May 2018 14:55:38 -0500
From:   Segher Boessenkool <segher@...nel.crashing.org>
To:     Christophe Leroy <christophe.leroy@....fr>
Cc:     linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
        netdev@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v3] powerpc: Implement csum_ipv6_magic in assembly

On Thu, May 24, 2018 at 10:18:44AM +0000, Christophe Leroy wrote:
> On 05/24/2018 06:20 AM, Christophe LEROY wrote:
> >Le 23/05/2018 à 20:34, Segher Boessenkool a écrit :
> >>On Tue, May 22, 2018 at 08:57:01AM +0200, Christophe Leroy wrote:
> >>>The generic csum_ipv6_magic() generates a pretty bad result
> >>
> >><snip>
> >>
> >>Please try with a more recent compiler, what you used is pretty ancient.
> >>It's not like recent compilers do great on this either, but it's not
> >>*that* bad anymore ;-)
> 
> Here is what I get with GCC 8.1
> It doesn't look much better, does it ?

There are no more mfocrf, which is a big speedup.  Other than that it is
pretty lousy still, I totally agree.  This improvement happened quite a
while ago, it's fixed in GCC 6.


Segher