i'm playing with kgdb and in the process have been learning/writing up little 
code snippets to make debugging easier ... for example, a small function that 
will dump the dmesg buffer in kgdb ... now, the issue at hand isnt kgdb :)

consider this simple function:
define speed-test
	shell date
	set $start = 1
	set $end = 3000
	while ($start != $end)
		set $start = $start + 1
	end
	printf "DONE\n"
	shell date
end

gives me these results with gdb-6.5:
(gdb) speed-test
Thu Aug 10 16:27:05 EDT 2006
DONE
Thu Aug 10 16:27:05 EDT 2006
(gdb) file vmlinux
Reading symbols from vmlinux...done.
(gdb) speed-test
Thu Aug 10 16:27:30 EDT 2006
DONE
Thu Aug 10 16:27:47 EDT 2006

this is done on an AMD64 Opteron 252 (~2.6gigz) so speed shouldnt be an 
issue :)
-mike