[luatex] LuaLaTeX's performance

[Khaled Hosny]

On Fri, Nov 19, 2010 at 08:52:39PM +0100, Pander wrote:
> Hi all,
> 
> I'm new here so please forgive my lacking knowledge of LuaLaTeX.
> 
> I'm compiling a font catalogue in XeLaTeX but am more and more compelled
> to switch over to LuaLaTeX because of better font support.
> 
> At the moment, only two things are obstructing this. First is missing
> support for polyglossia, but as I gathered, people are working on this.

AFAIK no one is actually working on that.

> The other thing is the performance. Now it could be that the current
> executable is not optimised and is doing loads of debug logging.
> However, my font catalogue is a good test case.
> 
> XeLaTeX can process it in two parts because other it runs out of memory.
> However, LuaLaTeX is hitting some sort of performance barrier halfway my
> document and after using up almost 6 GB of memory I have to kill off the
> process. Please see attached screenshots of memory usage.

LuaTeX will happily use all memory available to it (unlike most other
TeX engines which have hard-coded memory limit, IIUC). The current font
loading code is not very memory efficient and for certain fonts e.g.
fonts with huge kerning tables (some font developers like to say their
fonts have tens of thousands of kerning pairs, like if it is a feature
or something). I think post-texlive2010 releases of luatex made some
progress in this area, but I'm not sure if Hans started making use of it
or not.

> How can LuaLaTeX's performance be improved? Is the current executable in
> TLContrib a debug build with maximum logging?

I don't think so, I don't think it would be that relevant either. If you
can isolate the most offending fonts it might help in identifying and
possibly fixing the cause.

Regards,
 Khaled

-- 
 Khaled Hosny
 Arabic localiser and member of Arabeyes.org team
 Free font developer