linux-kernel - Re: [PATCH crypto 1/2] lib/crypto: blake2s-generic: reduce code size on small systems

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Message-ID: <CAMuHMdWOheM0WsHNTA2dS=wJA8kXEYx6G78bnZ51T1X8HWdzNg@mail.gmail.com>
Date:   Wed, 12 Jan 2022 11:57:49 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, wireguard@...ts.zx2c4.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>, Theodore Tso <tytso@....edu>,
        Greg KH <gregkh@...uxfoundation.org>,
        jeanphilippe.aumasson@...il.com, Ard Biesheuvel <ardb@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: Re: [PATCH crypto 1/2] lib/crypto: blake2s-generic: reduce code size
 on small systems

Hi Jason,

On Tue, Jan 11, 2022 at 2:49 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
> Re-wind the loops entirely on kernels optimized for code size. This is
> really not good at all performance-wise. But on m68k, it shaves off 4k
> of code size, which is apparently important.

On arm32:

add/remove: 1/0 grow/shrink: 0/1 up/down: 160/-4212 (-4052)
Function                                     old     new   delta
blake2s_sigma                                  -     160    +160
blake2s_compress_generic                    4872     660   -4212
Total: Before=9846148, After=9842096, chg -0.04%

On arm64:

add/remove: 1/2 grow/shrink: 0/1 up/down: 160/-4584 (-4424)
Function                                     old     new   delta
blake2s_sigma                                  -     160    +160
e843419@...0_00007634_e8a0                     8       -      -8
e843419@...1_0000423a_178c                     8       -      -8
blake2s_compress_generic                    5088     520   -4568
Total: Before=32800278, After=32795854, chg -0.01%

> Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>

For the size reduction:
Tested-by: Geert Uytterhoeven <geert@...ux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds