Tcl/Tk slowness on Linux

Hi,

As I've told several people some time ago, there seems to be a strange
slow-down problem with Tcl/Tk interaction (e.g. display_matrix, but also
just output into the toplevel window) on some machines (it turns out, all
Linux machines --- old and new farms, plus thames/alpha_linux).

Usually the amount of I/O or whatever is sufficiently small that one doesn't
notice it, but in some cases it becomes painfully obvious.  The bizarre
thing is that if one waves the mouse over the affected window, it runs
faster!

As a good example of a program where the difference is glaringly obvious, cd
to /homes/wh/src/slither, start TkEclipse, compile the files slither.ecl and
slither01.ecl, and then execute the goal `squares01(S), main(S, H, V).'  On
tempest, the program finds a solution and prints it using about 11 CPU
seconds, and not much longer elapsed time.  On an old farm machine it takes
about 6 CPU seconds, but left to its own devices (i.e. no helpful mouse
waving), the elapsed time is ... (aw hell after 10 minutes I lost patience
and "waved" it through to the end).  Monitoring the process with `top', it
was consistently using less than 1% of the CPU.

(These tests done using the default installed 5.2 version of TkEclipse, but
the problem also manifests with current builds of 5.3.)

Cheers,
Warwick