Huge files slow Emacs?

[塩野＠遊び人]

Hello,

I'm troubled with the most recent Emacs CVS getting slowed down in the
Solaris host.  I always make Emacs load a huge file (45MB or larger!)
in order to read mails with VM.  In such a condition, C-n and C-p take
about a second to move the point in every buffer, for example.

I had no dissatisfaction formerly even in a similar condition.  Though
I'm not sure what causes the problem, I tried several versions of the
sources of the past and realized there's no problem before a certain
period.  A doubtful change is the following (removing it solves the
problem):

        * dispextern.h (xassert): Enable unconditionally.

I appreciate anyone looking into it.

Best regrads,