linux-kernel - Re: [PATCH] crypto: twofish - add x86

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Date:	Wed, 15 Aug 2012 11:42:16 +0300
From:	Jussi Kivilinna <jussi.kivilinna@...et.fi>
To:	Johannes Goetzfried 
	<Johannes.Goetzfried@...ormatik.stud.uni-erlangen.de>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	Tilo Müller 
	<tilo.mueller@...ormatik.uni-erlangen.de>
Subject: Re: [PATCH] crypto: twofish - add x86_64/avx assembler
 implementation

Quoting Johannes Goetzfried  
<Johannes.Goetzfried@...ormatik.stud.uni-erlangen.de>:

> This patch adds a x86_64/avx assembler implementation of the Twofish block
> cipher. The implementation processes eight blocks in parallel (two 4 block
> chunk AVX operations). The table-lookups are done in general-purpose  
> registers.
> For small blocksizes the 3way-parallel functions from the twofish-x86_64-3way
> module are called. A good performance increase is provided for blocksizes
> greater or equal to 128B.
>
> Patch has been tested with tcrypt and automated filesystem tests.
>
> Tcrypt benchmark results:
>
> Intel Core i5-2500 CPU (fam:6, model:42, step:7)

I started thinking about the performance on AMD Bulldozer.  
vmovq/vmovd/vpextr*/vpinsr* between FPU and general purpose registers  
on AMD CPU is alot slower (latencies from 8 to 12 cycles) than on  
Intel sandy-bridge (where instructions have latency of 1 to 2). See:  
http://www.agner.org/optimize/instruction_tables.pdf

It would be really good, if implementation could be tested on AMD CPU  
to determinate, if it causes performance regression. However I don't  
have access to machine with such CPU.

-Jussi

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