Long delay after M-x commandname

[Eduardo Ochs <eduardoochs@gmail.com>]

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'.

What do I need to learn to understand what is going on, and to prepare
a proper bug report? A quick grepping shows that this message is
generated by `execute-extended-command' in simple.el, but what else?

  Thanks in advance,
    Eduardo Ochs
    http://angg.twu.net/#eev