linux-kernel - Re: [PATCH] poly1305: generic C can be faster on chips with slow unaligned access

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Message-ID: <20161103004934.GA30775@gondor.apana.org.au>
Date:   Thu, 3 Nov 2016 08:49:34 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        linux-crypto@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Martin Willi <martin@...ongswan.org>
Subject: Re: [PATCH] poly1305: generic C can be faster on chips with slow
 unaligned access

On Wed, Nov 02, 2016 at 11:00:00PM +0100, Jason A. Donenfeld wrote:
>
> Just tested. I get a 6% slowdown on my Skylake. No good. I think it's
> probably best to have the two paths in there, and not reduce it to
> one.

FWIW I'd rather live with a 6% slowdown than having two different
code paths in the generic code.  Anyone who cares about 6% would
be much better off writing an assembly version of the code.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt