[XeTeX] slow typesetting with fontspec

[Florian Grammel]

Dear list,

using the new fontspec-feature

\addfontfeature{LetterSpace=5.0}STUAGNL\addfontfeature{LetterSpace=0.0}

to letterspace all-capital acronyms (very nice indeed!), typesetting  
of my document gets unbelievably slow. My 300-pages that took 1 1/2  
min on my 1.33Ghz G4 without letter-spacing, take more than 15 min now.

The log-file gets blown up to monstrous 9MB, mainly filled with  
chunks of

...
Package fontspec Info: \font is "Junicode/BI:mapping=tex- 
text,letterspace=5.0,l
etterspace=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letterspa 
ce=0.0,
letterspace=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,lettersp 
ace=5.0
,letterspace=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letters 
pace=0.
0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,letter 
space=5
. 
0,letterspace=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letter 
space=
0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,lett 
erspace
=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,let 
terspac
e=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,le 
tterspa
ce=5.0,letterspace=0.0,letterspace=5.0,letterspace=0.0,letterspace=5.0,l 
ettersp
ace=0.0," on input line 85.
...

That made me wonder: Is it possible, that it is actually the  
compiling of the log that delays the typesetting? And if so: Is there  
a possibility to reduce the things written to the log or even to turn  
logging off completely?


Thanks in advance and best regards,
Florian.