Re: [PATCH v2 0/2] fsmonitor inline / testing cleanup

[Nipunn Koorapati <nipunn1313@gmail.com>]

> from Taylor
> I'm still iffy on whether or not this series makes sense to apply
> without the rest of the code that depends on it

Sorry for confusion. I don't think we should assume there is more code coming
related to this. I think this is intended to stand on its own.
It's not a required dependency either. Rather, it's motivated by
simplicity
- remove the dir.h dependency from fsmonitor.h.
- Keep implementation in fsmonitor.c and definitions in fsmonitor.h

> From Junio
> Those without fsmonitor would pay the call/return cost for no good
> reason if core_fsmonitor is not set, and checking that on the caller
> side may make a big difference.  How big?  That needs measurement.

Noted! This is not called out or measured - it is simply assumed based
on earlier
conversation. I should be able to run the fsmonitor perf suite before/after this
change and include the results in the commit message.

> This is a tangent, but with or without inlining, I find it iffy to
> see that untracked_cache_invalidate_path() is called only when
> fsmonitor is in use.  Does untracked_cache depend on fsmonitor for
> its correct operation?  Why is it OK not to invlidate when the
> caller would tell fsmonitor that a path is invalid if fsmonitor were
> in use?  The call is a statement of fact that the path is no longer
> valid, and that bit of information would be useful to the parts of
> the system outside fsmonitor, no?  Puzzled....

I did some source diving in an attempt to understand what's happening here.
I believe that untracked_cache_invalidate_path() is called in dir.c
whenever an entry is added or removed from
a directory.
This is an additional call when fsmonitor is enabled - because
fsmonitor's whole purpose
is to avoid the lstat on the other path. There is a nice explanation
in the original commit message

Commit 883e248b (fsmonitor: teach git to optionally utilize a file
system monitor to speed up detecting new or changed files.,
2017-09-22)

--Nipunn