From: Kees Cook <kees@kernel.org>
To: Colin Ian King <colin.i.king@gmail.com>
Cc: linux-hardening@vger.kernel.org, kernel-janitors@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH][next] fortify: add branch hints on unlikely fortify_panic paths
Date: Fri, 27 Jun 2025 09:36:23 -0700 [thread overview]
Message-ID: <202506270935.283087E22D@keescook> (raw)
In-Reply-To: <20250625161221.295575-1-colin.i.king@gmail.com>
On Wed, Jun 25, 2025 at 05:12:20PM +0100, Colin Ian King wrote:
> Analysis with gcov while running the stress-ng urandom stressor
> shows that there are a couple of fortify panic paths that are highly
> unlikely to be executed for well-behaving code. Adding appropriate
> branch hints improves the stress-ng urandom stressor my a small
> but statistically measureable amount. Ran 100 x 1 minute tests and
> measured the stressor bogo-op rates on a Debian based Intel(R)
> Core(TM) Ultra 9 285K with a 6.15 kernel with turbo disabled to
> reduce jitter.
>
> Results based on a Geometic Mean of 100 tests:
>
> Without patch: 50512.95 bogo-ops/sec
> With patch: 50819.58 bogo-ops/sec
>
> %Std.Deviation of ~0.18%, so low jitter in results, improvement of ~0.6%
>
> Signed-off-by: Colin Ian King <colin.i.king@gmail.com>
Nice find! It seems some ftrace configs are unhappy with this change,
though?
-Kees
--
Kees Cook
next prev parent reply other threads:[~2025-06-27 16:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-25 16:12 [PATCH][next] fortify: add branch hints on unlikely fortify_panic paths Colin Ian King
2025-06-27 0:14 ` kernel test robot
2025-06-27 1:05 ` kernel test robot
2025-06-27 16:36 ` Kees Cook [this message]
2025-06-27 16:47 ` Colin King (gmail)
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