Finding cpu time spent on my program

[jm.suresh@no.spam.gmail.com]

I am trying to measure the time the processor spends on some
operation, and I want this measure to not depend on the current load
of the machine. But doing the following prints different values each
time a run.

import time
c1 = time.clock()
for x in xrange(0xFFFFF): pass

c2 = time.clock()
print "Time spent is %f" % (c2-c1)

Is there a way to measure the number of cpu cycles spent on my program
alone irrespective of the current load etc of the machine.

-
Suresh