Strange slowness when killing words interactively

[Taylor Venable]

Hi, I'm having a strange problem with C-<backspace>
(backward-kill-word) and looking for some help in trying to debug it.
When I use this keystroke, the CPU usage spikes. The same goes for
C-<delete> (forward-kill-word) or any other key that I bind to either
of these functions. Other functions, such as backward-kill-sexp and
backward-kill-sentence, are similarly problematic. As a result, when I
hold the key down, my high repeat rate makes Emacs unresponsive for a
second until whatever is slowing down catches up. It happens with the
GTK GUI, but not with the text user interface. None of my other
machines have this behaviour with the same version of Emacs (that
includes one machine which is running the same distribution [Arch
Linux] with the same packages). No other programs on this system are
affected by performance problems when deleting words of text from a
block. The problem occurs with and without using -q. There does not
seem to be the same problem if I run the kill function itself with
C-u; for example, C-u 1000 backward-kill-word is instant. What's the
best way to profile this and figure out where my CPU cycles are being
eaten? Thanks for any help, my version information is below. I built
from fully updated bzr trunk tonight.

M-x emacs-version
GNU Emacs 24.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.22.1) of
2011-04-26

gcc --version
gcc (GCC) 4.6.0 20110415 (prerelease)

uname -a
Linux system76 2.6.38-ARCH #1 SMP PREEMPT Sun Apr 17 15:18:58 CEST
2011 x86_64 Intel(R) Core(TM) i7 CPU 870 @ 2.93GHz GenuineIntel
GNU/Linux

-- 
Taylor C. Venable
http://metasyntax.net/