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Date: Mon, 1 Dec 2014 16:16:18 -0800
Message-ID: <CAJBj3vew3K-A1sze0oZSQiTnd3prqv8S+7HP2bCU0w9gWLCgoQ@mail.gmail.com>
Subject: Re: [RFC PATCH] Btrfs: add sha256 checksum option
From: John Williams <jwilliams4200@gmail.com>
To: Alex Elsayed <eternaleye@gmail.com>
Cc: Btrfs BTRFS <linux-btrfs@vger.kernel.org>
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On Mon, Dec 1, 2014 at 4:06 PM, Alex Elsayed <eternaleye@gmail.com> wrote:
> https://github.com/openssl/openssl/blob/master/crypto/sha/asm/sha1-armv8.pl
>
> #             hardware-assisted software(*)
> # Apple A7    2.31              4.13 (+14%)
> # Cortex-A53  2.19              8.73 (+108%)
> # Cortex-A57  2.35              7.88 (+74%)


Note that those are showing 2 cycles per byte.

> From the CityHash readme, on a Xeon X5550 (which is _considerably_ more
> powerful than any of the above):
>
> On a single core of a 2.67GHz Intel Xeon X5550, CityHashCrc256 peaks at
> about 5 to 5.5 bytes/cycle.

5 bytes per cycle is 0.2 cycles per byte. So your own citation shows
that CityHash is 10 times faster.