Re: [Emacs-diffs] master 55ec674: * lisp/multifile.el: New file, extracted from etags.el

[Dmitry Gutov]

On 03.01.2019 3:37, Juri Linkov wrote:

> I tried with the latest c708231803 (at least ‘vc-log-mergebase’ shows
> that it's the latest), but optimized:
>
>        (dolist (f files)
>          (process-send-string process f)
>          (process-send-string process "\0"))
>
> was replaced with
>
>        (process-send-string process (mapconcat #'identity files "\0"))
>
> with no performance impact.

I tried this modification before, and it was slower, probably because of 
extra memory allocation. But on your machine it's probably hard to notice.

> Trying 446bcaed37 has no difference either.

That's unfortunate.

> Are you sure that project-find-regexp uses ‘find ... -path’?

Of course. What else would it be using to get the list of files?

It delegates to xref-collect-matches which, as you can see, builds a 
grep-find command. The salient difference is that find sends its output 
directly to grep, instead of going through Emacs.

> I see that slowness is because of many ‘-path’ filters used in project-files.o

*shrug*

It is indeed slower than 'git ls-files', and especially because of the 
filters, but see above.
> > At least test (split-string (shell-command-to-string "git ls-files -z") "\0" t)
>
> Using this instead of ‘(project-files (project-current t))’:
>
> (benchmark 10 '(project-files-pipe-grep "xyz1"))
> => 3s

So... I guess that's better. Have you tried running the same command in 
a terminal and timing it? I wonder how it compares. The terminal will 
show us the best possible speed.