bug#71094: [PATCH] Prefer to run find and grep in parallel in rgrep

[Dmitry Gutov]

On 22/05/2024 21:06, Manuel Giraud wrote:
> > I'd be happy if someone could time these methods on MS-Windows and on
> > some *BSD system, at least.  Bonus points for macOS.
> I'm not sure it is what you asked for but here is some numbers on
> OpenBSD (native 'find' and 'xargs'):
>
> $ time find ~/emacs-repo -type f -exec grep foo {} + > /dev/null
>      0m04.09s real     0m03.29s user     0m00.74s system
> $ time find ~/emacs-repo -type f -print0 | xargs -0 grep foo > /dev/null
>      0m04.10s real     0m03.45s user     0m00.66s system
>
> $ find /usr/src -type f | wc -l
>    114315
> $ time find /usr/src -type f -exec grep foo {} + > /dev/null
>      0m14.07s real     0m07.68s user     0m06.29s system
> $ time find /usr/src -type f -print0 | xargs -0 grep foo > /dev/null
>      0m13.83s real     0m07.94s user     0m06.25s system

I'm not sure how many matches for 'foo' are there inside your /usr/src, 
but if there are a lot, it slows down the last phase (grep output), 
making the performance gains a wash.

For this particular scenario, it's better to search for a string with no 
matches. Then you won't need to redirect to /dev/null too.