Re: [PATCH][next] fortify: add branch hints on unlikely fortify_panic paths

[Colin King (gmail)]

On 27/06/2025 17:36, Kees Cook wrote:
> 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@xxxxxxxxx>
>
> Nice find! It seems some ftrace configs are unhappy with this change,
> though?

I'll resend once I get some time to figure out the issues with the 
ftrace configs

Colin
> -Kees

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