Re: Too long completion delay time in LISP interaction mode.

[Tassilo Horn <tsdh@gnu.org>]

Hongyi Zhao <hongyi.zhao@gmail.com> writes:

>> First, I'd try to isolate where the slowdown happens.  The
>> screenshots suggests you are using company-mode with custom hacks to
>> get the numbering of candidates and you are using some fuzzy
>> completion-style.
>>
>> So I'd start with emacs -Q and typing (map<TAB> in *scratch* to get
>> the *Completions* buffer.  That will probably be fast but deliver
>> less results because of the default value of `completion-styles'.
>> Then I'd try out your settings of `completion-styles' (and
>
> `C-h o completion-styles RET'
>
> completion-styles is a variable defined in ‘minibuffer.el’.
>
> Its value is (hotfuzz)

Never heard of it.  But is it a suitable catch-all completion style,
i.e., suitable for using it without another more prefix-oriented style
preceeding it?  FWIW, when I type "(map", I'm most probably not
interested in having smartparens-mode, or
lsp:document-symbol-capabilities-hierarchical-document-symbol-support?
showing up as the top candidates but more in mapcar, mapc, mapcan, you
name it...

>> Also, using the profiler might shed some light on where the time is
>> spent, see (info "(elisp) Profiling").
>
> `M-x profiler-start RET cpu and mem RET'

I think you only need cpu here.

> Typeset (map) in scratch buffer, and then
>
> `M-x profiler-report RET', gives the following results:
>
>    262,542,852  87% - command-execute
>     262,542,852  87%  - funcall-interactively
>     262,538,196  87%   - counsel-M-x
>     262,538,196  87%    - let
>     262,355,940  87%     - ivy-read
>     262,355,940  87%      - apply
>     262,354,884  87%       + #<lambda 0x1b9d5ef2eb92a3f2>
>         182,256   0%     + counsel--M-x-externs

So the bottleneck is in the lambda which you didn't expand.  But I'm
also not sure if you are profiling the right thing because I don't think
that in-buffer completion (in terms of `completion-at-point-functions')
starts with M-x (or counsel-M-x).

Bye,
Tassilo