linux-kernel - Re: [PATCH v2 2/2] random: use BLAKE2s instead of SHA1 in extraction

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Message-ID: <CAHmME9pvGoPCL=KBJGa-3vZTY1Afshk0ccfGiL-zFVNHh1CjPA@mail.gmail.com>
Date:   Tue, 11 Jan 2022 14:00:44 +0100
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Theodore Tso <tytso@....edu>,
        Greg KH <gregkh@...uxfoundation.org>,
        Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>
Subject: Re: [PATCH v2 2/2] random: use BLAKE2s instead of SHA1 in extraction

On Tue, Jan 11, 2022 at 1:58 PM Geert Uytterhoeven <geert@...ux-m68k.org> wrote:
> Cool, much more than 1000 bytes:
>
> add/remove: 1/0 grow/shrink: 0/1 up/down: 160/-4032 (-3872)
> Function                                     old     new   delta
> blake2s_sigma                                  -     160    +160
> blake2s_compress_generic                    4448     416   -4032
> Total: Before=4227876, After=4224004, chg -0.09%
>
> I don't know what the impact is on performance, and if the compiler
> might do a good job unrolling this again when performance matters
> (i.e. if CONFIG_CC_OPTIMIZE_FOR_SIZE is not set).

Oh, wow, that's a lot indeed.

I guess the new code could be ifdef'd in a CONFIG_CC_OPTIMIZE_FOR_SIZE block?