bug#64735: 29.0.92; find invocations are ~15x slower because of ignores

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

>> >> Then how will the callback be different from
>> >> (mapc #'my-function (directory-files-recursively ...))
>> >> ?
>> >
>> > It depends on the application.  Applications that want to get all the
>> > data and only after that process it will not use the callback.  But I
>> > can certainly imagine an application that inserts the file names, or
>> > some of their transforms, into a buffer, and from time to time
>> > triggers redisplay to show the partial results.  Or an application
>> > could write the file names to some disk file or external consumer, or
>> > send them to a network process.
>> 
>> But won't the Elisp callback always result in a queue that will
>> effectively be synchronous?
>
> I don't understand the question (what queue?), and understand even
> less what you are trying to say here.  Please elaborate.

Consider (async-directory-files-recursively dir regexp callback) with
callback being (lambda (file) (start-process "Copy" nil "cp" file "/tmp/")).

`async-directory-files-recursively' may fire CALLBACK very frequently.
According to the other benchmarks in this thread, a file from directory
may be retrieved within 10E-6s or even less. Elisp will have to arrange
the callbacks to run immediately one after other (in a queue).
Which will not be very different compared to just running callbacks in a
synchronous loop.

-- 
Ihor Radchenko // yantar92,
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