From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: David Laight <David.Laight@aculab.com>
Cc: Eric Biggers <ebiggers@kernel.org>,
Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
Netdev <netdev@vger.kernel.org>,
WireGuard mailing list <wireguard@lists.zx2c4.com>,
LKML <linux-kernel@vger.kernel.org>, bpf <bpf@vger.kernel.org>,
Geert Uytterhoeven <geert@linux-m68k.org>,
"Theodore Ts'o" <tytso@mit.edu>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jean-Philippe Aumasson <jeanphilippe.aumasson@gmail.com>,
Ard Biesheuvel <ardb@kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: [PATCH crypto 1/2] lib/crypto: blake2s-generic: reduce code size on small systems
Date: Wed, 12 Jan 2022 23:00:48 +0100 [thread overview]
Message-ID: <CAHmME9p-JZS480-e3MvPsa1Q07rqX79h8oNEZsF970GjT-_nqA@mail.gmail.com> (raw)
In-Reply-To: <d7e206a5a03d46a69c0be3b8ed651518@AcuMS.aculab.com>
Hi David,
On 1/12/22, David Laight <David.Laight@aculab.com> wrote:
> I think you mentioned in another thread that the buffers (eg for IPv6
> addresses) are actually often quite short.
>
> For short buffers the 'rolled-up' loop may be of similar performance
> to the unrolled one because of the time taken to read all the instructions
> into the I-cache and decode them.
> If the loop ends up small enough it will fit into the 'decoded loop
> buffer' of modern Intel x86 cpu and won't even need decoding on
> each iteration.
>
> I really suspect that the heavily unrolled loop is only really fast
> for big buffers and/or when it is already in the I-cache.
> In real life I wonder how often that actually happens?
> Especially for the uses the kernel is making of the code.
>
> You need to benchmark single executions of the function
> (doable on x86 with the performance monitor cycle counter)
> to get typical/best clocks/byte figures rather than a
> big average for repeated operation on a long buffer.
>
> David
This patch has been dropped entirely from future revisions. The latest
as of writing is at:
https://lore.kernel.org/linux-crypto/20220111220506.742067-1-Jason@zx2c4.com/
If you'd like to do something with blake2s, by all means submit a
patch and include various rationale and metrics and benchmarks. I do
not intend to do that myself and do not think my particular patch here
should be merged. But if you'd like to do something, feel free to CC
me for a review. However, as mentioned, I don't think much needs to be
done here.
Again, v3 is here:
https://lore.kernel.org/linux-crypto/20220111220506.742067-1-Jason@zx2c4.com/
Thanks,
Jason
next prev parent reply other threads:[~2022-01-12 22:01 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAHmME9qbnYmhvsuarButi6s=58=FPiti0Z-QnGMJ=OsMzy1eOg@mail.gmail.com>
2022-01-11 13:49 ` [PATCH crypto 0/2] smaller blake2s code size on m68k and other small platforms Jason A. Donenfeld
2022-01-11 13:49 ` [PATCH crypto 1/2] lib/crypto: blake2s-generic: reduce code size on small systems Jason A. Donenfeld
2022-01-12 10:57 ` Geert Uytterhoeven
2022-01-12 13:16 ` Jason A. Donenfeld
2022-01-12 18:31 ` Eric Biggers
2022-01-12 18:50 ` Jason A. Donenfeld
2022-01-12 21:27 ` David Laight
2022-01-12 22:00 ` Jason A. Donenfeld [this message]
2022-01-11 13:49 ` [PATCH crypto 2/2] lib/crypto: blake2s: move hmac construction into wireguard Jason A. Donenfeld
2022-01-11 14:43 ` Ard Biesheuvel
2022-01-12 18:35 ` Eric Biggers
2022-01-11 18:10 ` [PATCH crypto v2 0/2] reduce code size from blake2s on m68k and other small platforms Jason A. Donenfeld
2022-01-11 18:10 ` [PATCH crypto v2 1/2] lib/crypto: blake2s: move hmac construction into wireguard Jason A. Donenfeld
2022-01-11 18:10 ` [PATCH crypto v2 2/2] lib/crypto: sha1: re-roll loops to reduce code size Jason A. Donenfeld
2022-01-11 22:05 ` [PATCH crypto v3 0/2] reduce code size from blake2s on m68k and other small platforms Jason A. Donenfeld
2022-01-11 22:05 ` [PATCH crypto v3 1/2] lib/crypto: blake2s: move hmac construction into wireguard Jason A. Donenfeld
2022-01-11 22:05 ` [PATCH crypto v3 2/2] lib/crypto: sha1: re-roll loops to reduce code size Jason A. Donenfeld
2022-01-12 10:59 ` [PATCH crypto v3 0/2] reduce code size from blake2s on m68k and other small platforms Geert Uytterhoeven
2022-01-12 13:18 ` Jason A. Donenfeld
2022-01-18 6:42 ` Herbert Xu
2022-01-18 11:43 ` Jason A. Donenfeld
2022-01-18 12:44 ` David Laight
2022-01-18 12:50 ` Jason A. Donenfeld
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