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

[Eli Zaretskii <eliz@gnu.org>]

> Date: Wed, 22 May 2024 17:50:42 +0300
> Cc: sbaugh@janestreet.com, 71094@debbugs.gnu.org, rgm@gnu.org
> From: Dmitry Gutov <dmitry@gutov.dev>
> 
> >> Whereas in the Emacs repository "find ... -print0 | wc" reports 202928
> >> characters. Meaning, it uses just 1.5 'grep' invocations. To see better
> >> parallelism there we'll need to either lower the limit or test it in a
> >> project at least twice as big.
> > 
> > ...until xargs collects all those characters, it will not invoke grep,
> > right?  So, for directories whose file names total less than those
> > 200K, xargs will still wait until find ends its job, right?
> 
> That's right. And it's why we're not seeing much of a difference in 
> projects of Emacs's size or smaller. No apparent regression either, though.

But we added xargs to the soup.  On GNU/Linux, where GNU Findutils are
developed, it probably isn't a problem.  On other systems, not
necessarily...

> >> So here is another example: a Linux kernel checkout (76K files). Also
> >> about 30% improvement: 1.40s vs 2.00s.
> > 
> > This is all highly system-dependent.
> 
> Naturally. So it'd be great to see some additional data points from 
> users on other systems.
> 
> Especially those where the default limit is lower than it is on mine.

I'd be happy if someone could time these methods on MS-Windows and on
some *BSD system, at least.  Bonus points for macOS.