[IronPython] weird performance issue

Kamil Dworakowski kamil at dworakowski.name
Tue Dec 16 20:07:55 CET 2008


We see a very strange side effect of running the follwing code on the
performance of recalculations in Resolver One.

def Dumbcorator(fn):
    def _inner(self, *args):
        return fn(self, *args)
    return _inner

class Locker(object):
    @property
    @Dumbcorator
    def thing(self):
        return 2

l = Locker()
l.thing

Specifically, one of the performance test reports results 4 to 8 times
worse with this snippet in than without (the clock is turned on after
this snippet executes). If I comment out this snippet from the code,
it suddenly runs 4 to 8 times faster. The fact that I can comment it
out means that it is not used in the test, so it is bizzare that it
slows it down.

We can't reproduce the slow down in a clean example though. I hope
something clicks for somebody and gives me a hint as to what is going
on. Tomorrow I'll continue on trying to minimize the code that is
being slowed down, and hopefully come up with some decent repro.



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