Re: Long delay after M-x commandname

[Stefan Monnier]

Eduardo Ochs [2021-10-10 21:45:39] wrote:

> Hi list,
>
> this is not a bug report YET - I am looking for more information
> first.
>
> Yesterday I noticed that when I was invoking commands with M-x
> commandname and using tab for completing parts of the name then
> sometimes there would be a long delay - sometimes as long as 10
> seconds, but my laptop is quite old - between the RET and the
> execution of the command. This delay was big on emacs28 and
> practically imperceptible on emacs27. I have several versions of
> emacs28 here, with names like emacs28_512 for the one correponding to
> HEAD~512 and emacs28_0 for HEAD, and I noticed that this delay was
> growing in recent versions: small in HEAD~256, bigger in HEAD~128,
> much bigger in HEAD~0.
>
> I _guess_ that these delays are caused by the code that generates
> messages like this one:
>
>   You can run the command `find-eev-install-intro' with `M-x f--i-i'.

This message can be suppressed with `extended-command-suggest-shorter`.

It can take work to find that shortest replacement (it's a kind of
brute-force algorithm which tries all combinations of increasing length
until one works), indeed, tho usually it's negligible.  I'm surprised
the time taken has changed significantly recently  That code has been
the same Emacs-26, AFAIK.  The completion data has an impact on the
performance, so maybe that's what's going on, but it still seems
surprising you'd see such a progressive slowdown.


        Stefan