Re: Improving Emacs performance on Cygwin

[Davis Herring]

> I would like to apply the following patch, which seems to give a
> substantial performance improvement on Cygwin (and obviously has no
> effect on other platforms).
> [...]
>   #define DIRENTRY_NONEMPTY(p) ((p)->d_name[0] != 0)
>   #else
>   #define DIRENTRY_NONEMPTY(p) ((p)->d_ino)

How can looking up d_name[0] be any slower than looking up d_ino?  They're
both already in memory (d_name is an array, not a pointer, even); are we
really seeing a "substantial performance improvement" from a cache effect
or something?

This is a question born of curiosity, not a criticism; so long as the
relevant version of Cygwin is properly handled (as addressed elsewhere in
the thread) simplifying the conditional is already a win.

Davis

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