linux-kernel - Re: [PATCH 2/3] [CRYPTO] Add optimized SHA-1 implementation for i486+

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Date:	Sat, 9 Jun 2007 15:11:59 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Benjamin Gilbert <bgilbert@...cmu.edu>
Cc:	akpm@...ux-foundation.org, herbert@...dor.apana.org.au,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] [CRYPTO] Add optimized SHA-1 implementation for i486+

On Fri, Jun 08, 2007 at 05:42:53PM -0400, Benjamin Gilbert wrote:
> Add x86-optimized implementation of the SHA-1 hash function, taken from
> Nettle under the LGPL.  This code will be enabled on kernels compiled for
> 486es or better; kernels which support 386es will use the generic
> implementation (since we need BSWAP).
> 
> We disable building lib/sha1.o when an optimized implementation is
> available, as the library link order for x86 (and x86_64) would otherwise
> ignore the optimized version.  The existing optimized implementation for ARM
> does not do this; the library link order for that architecture appears to
> favor the arch/arm/ version automatically.  I've left this situation alone
> since I'm not familiar with the ARM code, but a !ARM condition could be
> added to CONFIG_SHA1_GENERIC if it makes sense.
> 
> The code has been tested with tcrypt and the NIST test vectors.

Have you benchmarked this against lib/sha1.c? Please post the results.
Until then, I'm frankly skeptical that your unrolled version is faster
because when I introduced lib/sha1.c the rolled version therein won by
a significant margin and had 1/10th the cache footprint.

-- 
Mathematics is the supreme nostalgia of our time.
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