linux-kernel - Re: [PATCH v2 2/2] powerpc32: optimise csum

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Message-ID: <55D1BED4.4040808@c-s.fr>
Date:	Mon, 17 Aug 2015 13:00:36 +0200
From:	leroy christophe <christophe.leroy@....fr>
To:	Segher Boessenkool <segher@...nel.crashing.org>,
	Scott Wood <scottwood@...escale.com>
CC:	Paul Mackerras <paulus@...ba.org>, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] powerpc32: optimise csum_partial() loop



Le 17/08/2015 12:56, leroy christophe a écrit :
>
>
> Le 07/08/2015 01:25, Segher Boessenkool a écrit :
>> On Thu, Aug 06, 2015 at 05:45:45PM -0500, Scott Wood wrote:
>>> If this makes performance non-negligibly worse on other 32-bit 
>>> chips, and is
>>> an important improvement on 8xx, then we can use an ifdef since 8xx 
>>> already
>>> requires its own kernel build.  I'd prefer to see a benchmark 
>>> showing that it
>>> actually does make things worse on those chips, though.
>> And I'd like to see a benchmark that shows it *does not* hurt 
>> performance
>> on most chips, and does improve things on 8xx, and by how much. But it
>> isn't *me* who has to show that, it is not my patch.
> Ok, following this discussion I made some additional measurement and 
> it looks like:
> * There is almost no change on the 885
> * There is a non negligeable degradation on the 8323 (19.5 tb ticks 
> instead of 15.3)
>
> Thanks for pointing this out, I think my patch is therefore not good.
>
Oops, I was talking about my other past, the one that was to optimise 
ip_csum_fast.
I still have to measure csum_partial

Christophe
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