[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: State of the overlay tree branch?
From: |
Eli Zaretskii |
Subject: |
Re: State of the overlay tree branch? |
Date: |
Mon, 19 Mar 2018 08:28:22 +0200 |
> From: Sebastian Sturm <address@hidden>
> Date: Sun, 18 Mar 2018 22:04:13 +0100
>
> I also found it surprising that overlays would slow down line counting,
> but since I don't know anything about the architecture of the Emacs
> display engine, or its overlay implementation, I figured that overlays
> must be to blame because
>
> (i) the issue went away after switching to the feature/noverlay branch
>
> (ii) configuring the semantic highlighter to use its font-lock backend
> also resolved the performance issue (though with the font-lock backend,
> highlights are easily messed up by editing operations which makes the
> overlay variant far more appealing)
If you look at the implementation of count-lines, you will see it just
calls forward-line, which pays no attention to overlays (as I'd
expect).
> I also found that some other heavy users of overlays such as
> avy-goto-word-0-{above,below} feel faster with the feature/noverlay
> branch, so I'd welcome a merge of the overlay branch even if there was a
> technically superior alternative to line-number-at-pos that didn't
> suffer from overlay-related performance issues.
That's unrelated: we want to merge that branch when it's ready for
several good reasons. But counting lines shouldn't be one of those
reasons.
> That being said, your suggestion sounds intriguing. What would be
> required to expose find_newline to Lisp? Would I simply have to wrap it
> in one of Emacs's DEFINE_<something> macros?
DEFUN, more accurately. But yes.
Actually, I see that forward-line already calls find_newline almost
directly, so it should be fast enough. Exposing find_line should
perhaps be able to produce some speedup (because you don't need to set
point, like forward-line does), but I doubt that it would be
significant.
> Is there some documentation on the Emacs C backend?
There's the "Writing Emacs Primitives" section of the "Internals"
appendix.
Turning back to your original problem, viz.:
>> [1] I'm using cquery for my C++ editing needs, which comes with an
>> overlay-based semantic highlighting mechanism. With my emacs
>> configuration, lsp-mode/lsp-ui emit 6 calls to line-number-at-pos per
>> character insertion, which consume ~20 to 25 ms each when performing
>> edits close to the bottom of a 66KB C++ file (measured using
>> (benchmark-run 1000 (line-number-at-pos (point))) on a release build of
>> emacs-27/git commit #9942734...). Using the noverlay branch, this figure
>> drops to ~160us per call.
it looks strange to me that you get such long times. I just tried
Emacs 26.0.91 near the end of xdisp.c (a 1MB file with over 33K
lines), and I get 3 ms per call there. So I wonder how come you get 4
or 5 ms per call in a file that is 50 times smaller, because if I run
the above benchmark with point at 70K, I get 0.16 ms per call. In an
unoptimized build of the current master branch, I get 0.25 ms per call
under these conditions. (And you could cache the result if you need 6
calls in the same vicinity, and after the initial call only call
forward-line to compute relative increments.)
This is with a 5-year old i7-2600 box with a 3.40 GHz clock. Is your
CPU significantly slower?
- Re: State of the overlay tree branch?, (continued)
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/23
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/23
- Re: State of the overlay tree branch?, Sebastian Sturm, 2018/03/23
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/23
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/23
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/23
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/23
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/19
- Re: State of the overlay tree branch?,
Eli Zaretskii <=
RE: State of the overlay tree branch?, Drew Adams, 2018/03/18
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/18
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/19
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/19
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/19
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/19
- Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/19
- Re: State of the overlay tree branch?, Stefan Monnier, 2018/03/19
Re: State of the overlay tree branch?, Eli Zaretskii, 2018/03/19
Re: State of the overlay tree branch?, Sebastien Chapuis, 2018/03/21