[XeTeX] xetex memory usage

[Jonathan Kew]

On 16 Dec 2008, at 19:53, basketboy at bk.ru wrote:

> Hello,
>
> I'm using MiKTeX 2.7 and xetex(xelatex) integrated in it. OS:  
> Windows XP
> SP3.
>
> My question is about memory usage of xetex. I've noticed that when I
> compile tex document, though this:
>
> \documentclass{article}
> \usepackage{fontspec}
> \setmainfont{Arial}
> \begin{document}
> The quick brown fox jumps over the lazy dog.
> \textbf{The quick brown fox jumps over the lazy dog.}
> \emph{The quick brown fox jumps over the lazy dog.}
> \end{document}
>
>
> I see that it uses at least 130MB of RAM to generate pdf. So if for
> example I'm going to use xetex to generate pdf reports via webpage it
> can cause memory overusage. For example if 10 people start to generate
> pdfs simultaneously then 1300Mb of RAM will be used and it can cause  
> the
> problems. We run into this problem already (with much more complex tex
> documents) and server with 512 MB of RAM and it was overloaded.
>
> So my questions are the following:
>
> 1. Is this problem related with xetex or maybe fonts loading into
> memory? If it is not related to xetex then sorry, I'll try to find
> answer from MiKTeX users.

The RAM footprint is much larger than standard 8-bit TeX because many  
internal tables have been expanded to cover the full Unicode range of  
characters -- approximately one million, as compared to 256  
characters. Using over 100MB is not generally a problem on modern  
hardware; much of this memory is not actively used in a typical run,  
and so virtual memory systems need not even keep it in real RAM, but  
it does get allocated at startup.

>
> 2. Is it possilbe to reduce RAM consumption in this case?

Not with the existing program. Many of the internal arrays could be  
made much smaller by using a smarter "sparse array" implementation  
instead of simple flat arrays. This has not been a priority for me, as  
users do not normally need to run large numbers of xetex processes in  
parallel, but if someone wants to provide such a patch it would be  
welcome.

Actually, you could reduce the RAM footprint quite a bit by reducing  
various parameters in texmf.cnf (for TeX Live; I don't know if MikTeX  
uses a similar configuration file), as the default settings (at least  
with TL) are extremely generous, and most documents can be processed  
within much smaller limits.

JK