Re: [PATCH 3/3] core: convert build-time USE_NSEC into runtime core.useNanosec

On Sat, Aug 8, 2026 at 12:31 PM SZEDER Gábor <[email protected]> wrote:
>
> On Fri, Aug 07, 2026 at 02:17:39PM -0700, Junio C Hamano wrote:
> > "D. Ben Knoble" <[email protected]> writes:
> >
> > > Racy Git problems persist today, manifesting themselves in the
> > > performance of commands like "git diff" in new worktrees [1]. We have
> > > long had a build knob "USE_NSEC" to tell Git to use in-core nanosecond
> > > precision when available, which mitigates most if not all racy issues,
> > > but most builds we know about it don't use it. In part, that's because
> > > someone distributing Git can't safely enable it at compile-time if they
> > > don't know exactly what platforms their distribution will be used on.
> > >
> > > [1]: https://lore.kernel.org/git/CALnO6CADMJSixqYvL1Yo8qKX5rWhKQ+2OoSEuPUh-yoeK9TseQ@mail.gmail.com
> > >
> > > These days, most platforms are likely to be safe for the USE_NSEC code.
> > > Regardless, we want to give users the ability to benefit from it. This
> > > requires exposing the compile-time gated code as a runtime option.
> > >
> > > In addition, update the Racy Git documentation and other mentions of
> > > USE_NSEC in the code.
> > >
> > > Best-viewed-with: --ignore-space-change
> >
> > Don't do this.  It probably is helpful to have something like that
> > below the three-dash lines, though.
>
> Including this hint in the commit message could be useful for anyone
> who stumbles upon this commit in a couple of months or years time.
> Whether it should be a trailer or not is another question.

Yep, the trailer is a force-of-habit for me. I'll move it into the
commit message body in the next version.

I do find it helpful when the author of a patch---who presumably knows
the changes best---provides some guidance on making sense of the diff.
In this case, some code is re-indented as '#ifdef's change to runtime
'if's, so ignoring whitespace changes makes it easier to see there was
no change there.

-- 
D. Ben Knoble