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

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Message-ID: <CAHmME9ogYTGFaNDt1CD0FxEHxDzVhNX=AN3_PH3t=0zREGgYPA@mail.gmail.com>
Date:   Wed, 2 Nov 2016 23:00:00 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
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 2, 2016 at 10:26 PM, Herbert Xu <herbert@...dor.apana.org.au> wrote:
> What I'm interested in is whether the new code is sufficiently
> close in performance to the old code, particularonly on x86.
>
> I'd much rather only have a single set of code for all architectures.
> After all, this is meant to be a generic implementation.

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.