Re: [RFC/PATCH v2 1/1] cygwin: Add fast_lstat() and fast_fstat() functions

Mark Levedahl wrote:

On 07/10/2013 04:23 PM, Ramsay Jones wrote:

quoted

Commit adbc0b6b ("cygwin: Use native Win32 API for stat", 30-09-2008)
added a Win32 specific implementation of the stat functions. In order
to handle absolute paths, cygwin mount points and symbolic links, this
implementation may fall back on the standard cygwin l/stat() functions.
Also, the choice of cygwin or Win32 functions is made lazily (by the
first call(s) to l/stat) based on the state of some config variables.

Unfortunately, this "schizophrenic stat" implementation has been the
source of many problems ever since. For example, see commits 7faee6b8,
79748439, 452993c2, 085479e7, b8a97333, 924aaf3e, 05bab3ea and 0117c2f0.

In order to limit the adverse effects caused by this implementation,
we provide a new "fast stat" interface, which allows us to use this
only for interactions with the index (i.e. the cached stat data).

Signed-off-by: Ramsay Jones <redacted>
---

I've tested this on Cygwin 1.7 on WIndows 7 , comparing to the results 
using your prior patch (removing the Cygwin specific lstat entirely) and 
get the same results with both, so this seems ok from me.

Thank you for testing this.

My comparison point was created by reverting your current patch from pu, 
then reapplying your earlier patch on top, so the only difference was 
which approach was used to address the stat functions.

Caveats:
1) I don't find any speed improvement of the current patch over the 
previous one (the tests actually ran faster with the earlier patch, 
though the difference was less than 1%).
2) I still question this whole approach, especially having this 
non-POSIX compliant mode be the default. Running in this mode breaks 
interoperability with Linux, but providing a Linux environment is the 
*primary* goal of Cygwin.

Yes, I agree. Since I _always_ disable the Win32 stat functions (by
setting core.filemode by hand - yes it's a little annoying), I don't
get any "benefit" from the added complexity.

However, I don't use git on cygwin with *large* repositories. git.git
is pretty much as large as it gets. So, the difference in performance
for me amounts to something like 0.120s -> 0.260s, which I can barely
notice.

Other people may not be so lucky ...

I would be happy if my original patch (removing the win32 stat funcs)
was applied, but others may not be. :-P

ATB,
Ramsay Jones