Re: File path completions: strange speed discrepancy

[Michael Albinus]

JD Smith <jdtsmith@gmail.com> writes:

Hi,

> Thanks very much for this much improved testing code (which also saves
> the tedium of slowly retyping!).  I altered it slightly to include a
> few more function, and target my local wired server:
>
> (progn
>  (require 'tramp-sh)
>  (tramp-cleanup-all-connections)
>  (elp-instrument-list '(file-exists-p completing-read
> read-file-name-internal read-file-name-default
> tramp-handle-file-name-completion
> tramp-sh-handle-file-name-all-completions))
>  (setq unread-command-events (mapcar 'identity
> "///ssh:datpi:/home/pi/no\tex\t/do\tma\tce\t\n"))
>  (call-interactively #'find-file)
>  (elp-results)
>  (elp-reset-all))

I've applied the same, except the remote file name.

My timing results (emacs -Q, v28.0.50):

>From *scratch*:

read-file-name-default                     1           9.064781548   9.064781548
completing-read                            1           9.057834631   9.057834631
tramp-handle-file-name-completion          3           8.331385864   
2.7771286213
tramp-sh-handle-file-name-all-completions  4           7.290909892   1.822727473
file-exists-p                              45          1.7296832099  
0.0384374046
read-file-name-internal                    13          0.4099991600  
0.0315383969

>From remote dired:

read-file-name-default                     1           8.23891833    8.23891833
completing-read                            1           8.228419034   8.228419034
tramp-handle-file-name-completion          3           7.4998795480  
2.4999598493
tramp-sh-handle-file-name-all-completions  4           6.463144493   
1.6157861232
file-exists-p                              45          1.6901479139  
0.0375588425
read-file-name-internal                    13          0.3952138859  
0.0304010681

> So really only very little difference inside the tramp completion
> functions; they seem to be doing the same job independent of the
> starting point.  But the completing-read itself, which is where
> find-file is spending its time, is taking 8x longer!  And
> read-file-name-internal is 35x slower.  Do you find this as well? 
> I’ll dig a bit deeper and see if I can narrow it down further. 

With Emacs 28, the differences aren't so relevant. The absolute time is
much higher than in your case, but I have taken "savannah" as test host
which is "far from me".

Do you have a chance to compile Emacs from git, and run the test?

Best regards, Michael.