Poor performance over DSL link

[Marc Levoy]

Dear Emacs maintainers,

I just upgraded from Emacs 20.7 to 21.2, and I am suddenly seeing high traffic
on my DSL link whenever the mouse is positioned over my Emacs window, even if
my hands are off the keyboard and mouse.  Under 20.7, if I didn't touch the
keyboard or mouse, there was no network traffic.  Emacs 21.2 seems sluggish
over a DSL link; could this be why?

More details:

I am running "GNU Emacs 21.2.1 (i386-redhat-linux-gnu, X toolkit, Xaw3d scroll
bars) of 2002-04-08 on porky.devel.redhat.com" on a Linux 7.3 system and
displaying through Exceed 7.0 to a Windows 2000 system.  However, I see
the same problem displaying through VNC, so I suspect the problem arises
from within Emacs.  (If I move the mouse off the Emacs window, the extra
traffic stops.)

I have tried turning off scroll bars and tooltips, but neither has any effect.
I have searched the Internet for similar reports, and I see various complaints
about the performance of various versions of Emacs over slow connections, but
nothing that seems relevant to fixing the problem.

Is there something else I can disable in order to stop this network traffic
and restore my editing performance?

-Marc Levoy
 Associate Professor
 Computer Science Department
 Stanford University