[luatex] Identifying why LuaTeX 2023 is slower than LuaTeX 2022

[luigi scarso]

On Mon, 28 Aug 2023 at 16:50, Paulo Roberto Massa Cereda <
cereda.paulo at gmail.com> wrote:

> Dear friends,
>
> I beseech your wisdom. :) In my tests, I noticed LuaTeX 2023 is
> significantly slower than the 2022 counterpart. Here's a MWE:
>
> --------8<--------
> Lorem ipsum dolor sit amet, consectetur adipiscing elit,
> sed do eiusmod tempor incididunt ut labore et dolore magna
> aliqua. Ut enim ad minim veniam, quis nostrud exercitation
> ullamco laboris nisi ut aliquip ex ea commodo consequat.
> Duis aute irure dolor in reprehenderit in voluptate velit
> esse cillum dolore eu fugiat nulla pariatur. Excepteur
> sint occaecat cupidatat non proident, sunt in culpa qui
> officia deserunt mollit anim id est laborum.
> \bye
> --------8<--------
>
> Benchmark 1: texlive/2022/bin/x86_64-linux/luatex test.tex
>   Time (mean ± σ):     177.7 ms ±   1.4 ms    [User: 140.9 ms, System:
> 36.6 ms]
>   Range (min … max):   175.8 ms … 180.3 ms    16 runs
>
> Benchmark 2: texlive/2023/bin/x86_64-linux/luatex test.tex
>   Time (mean ± σ):     286.7 ms ±   2.3 ms    [User: 246.1 ms, System:
> 40.3 ms]
>   Range (min … max):   284.0 ms … 291.2 ms    10 runs
>
> Summary
>   texlive/2022/bin/x86_64-linux/luatex test.tex ran
>     1.61 ± 0.02 times faster than texlive/2023/bin/x86_64-linux/luatex
> test.tex
>
> I initially had tried with LuaLaTeX and got similar results. Ulrike
> Fischer and Marcel Krüger kindly helped me find out what was going on,
> but we could not find anything relevant. I've tried:
>
> - loading a custom OTF font: 2022 was 1.53 ± 0.02 (cold cache) and
> 1.83 ± 0.03 (existing cache) times faster
> - loading the default OTF font: 2022 was 1.68 ± 0.02 (cold cache) and
> 2.02 ± 0.03 (existing cache) times faster
> - HarfBuzz: 2022 was 1.57 ± 0.02 times faster (cold cache) and 1.84 ±
> 0.05 times faster (existing cache)
> - raw feature (normalize): 2022 was 1.81 ± 0.03 times faster
> - updated luaotfload-tool in TL2022: 2022 was 1.83 ± 0.01 times faster
> - no OTF: 2022 was 1.95 ± 0.02 times faster
>
> I was wondering if someone could shed some light into this. :) Thanks!
>
>

I have done some quick tests (running luatex test.tex) and the wall clock
here is roughly 0.30s  in both cases
(luatex 2022 seems to be more near to 0.29 than 0.30).
Intel(R) Core(TM) i7-7500U CPU @ 2.70GHz, 24GB , HDD 5400rpm

--
luigi
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