[luatex] Why accessing font.fonts table is so slow?

[Khaled Hosny]

After struggling the whole day trying to figure out why my less than 300
lines of code are so slow, I found that all the slowness comes from
accessing font.fonts table, which would take from 0.02 to 0.07 seconds
each time, getting rid of that drops my test file from ~16 to ~2
seconds. Now I'm just wondering if this slowness is expected, and
wither it deserves a small warning in the manual (it would have saved my
day if I knew it beforehand), I read it is not a real table, but nothing
suggests the slowness I'm getting.

Regards,
 Khaled

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