Date: Sat, 9 Jun 2007 15:11:59 -0500
From: Matt Mackall <mpm@selenic.com>
To: Benjamin Gilbert <bgilbert@cs.cmu.edu>
Cc: akpm@linux-foundation.org, herbert@gondor.apana.org.au,
       linux-crypto@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] [CRYPTO] Add optimized SHA-1 implementation for i486+
Message-ID: <20070609201159.GC11166@waste.org>
References: <20070608214242.23949.30350.stgit@dev> <20070608214253.23949.40465.stgit@dev>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20070608214253.23949.40465.stgit@dev>
User-Agent: Mutt/1.5.13 (2006-08-11)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1467
Lines: 28

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.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/