Re: git-diff in a worktree is an order of magnitude slower?

["brian m. carlson" <sandals@crustytoothpaste.net>]

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On 2026-06-11 at 17:43:52, Junio C Hamano wrote:
> Jeff King <peff@peff.net> writes:
> 
> > I guess the distinction goes back to c06ff4908b (Record ns-timestamps if
> > possible, but do not use it without USE_NSEC, 2009-03-04), which details
> > some reasons you might not want USE_NSEC. Feels like it ought to be a
> > run-time config, though, and maybe even something that gets auto-probed
> > by git-init.
> 
> I thought for a bit but didn't think of a clean way to auto-probe if
> a filesystem loses nanosecond-precision part of .st_Xtime when
> "metadata is flushed and later read back in" with reasonable
> overhead.  I do not think we want to trigger system-wide sync and/or
> dropping of buffer cache ;-)

We could have `git update-index` take options like it does for
`--untracked-cache` and `--no-untracked-cache` to control these for
people who want them.  For instance, I know what operating system and
file system I'm using (Linux with btrfs), so if I know that option is
safe, I can enable it at runtime and reap the benefits.

We could even have `--test-use-nsec` to perform a `uname` and `statfs`
call to determine whether this is a known safe configuration if probing
is not possible.
-- 
brian m. carlson (they/them)
Toronto, Ontario, CA

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