[IronPython] weird performance issue

[Dino Viehland]

Oh, if you also want to get a list of call stacks to PythonContext.Call and send those our way that'd be useful as well.

In general we only want to hit that when the overall cost of whatever we're doing will dwarf any overhead of that one call.  And we certainly have more calls to it then we should :(

> -----Original Message-----
> From: users-bounces at lists.ironpython.com [mailto:users-
> bounces at lists.ironpython.com] On Behalf Of Kamil Dworakowski
> Sent: Wednesday, December 17, 2008 10:03 AM
> To: Discussion of IronPython
> Subject: Re: [IronPython] weird performance issue
>
> Thanks Dino, it looks like you are right. I print whenever
> _supportAdding == false.
> It happens a lot with the snippet executed, whereas it doesn't happen
> at all with
> the snippet commented out.
>
> We also discovered that the slow down only occurs when we compile code
> to dlls (no _supportAdding == false if runned from sources).
> Still can't come up with a repro though. If you provide us with a
> patch, we can
> test if it solves the problem in our code.
>
> As a short term solution we have removed all the properties from
> decorated functions. This fixed one performance test. We moved to
> other performance tests and we still see that some functions are
> slower when executed from dlls, so the same slow down might be
> triggered by sth else.
>
> On Wed, Dec 17, 2008 at 3:21 AM, Dino Viehland <dinov at microsoft.com>
> wrote:
> > My guess would be that we're pushing the PythonContext._callSplatSite
> outside of the sweet spot in DLR site caches.
> >
> > You could check this by putting a breakpoint in
> PythonContext.Call(object, params object[]).  Then look and see if
> _callSplatSite._rules is an instance of EmptyRuleSet<T> with
> _supportAdding == false.
> >
> > If this is the cause it should be pretty easy to fix - property's
> should probably get their own call site object so it'll be specialized
> to the specific property (maybe we could share a common one of the
> function is a PythonFunction as these generate highly shareable calls
> between multiple function instances).  We're also doing a params call
> today which we could stop doing and get a nice perf boost on
> properties.
> >
> >> -----Original Message-----
> >> From: users-bounces at lists.ironpython.com [mailto:users-
> >> bounces at lists.ironpython.com] On Behalf Of Kamil Dworakowski
> >> Sent: Tuesday, December 16, 2008 11:08 AM
> >> To: users at lists.ironpython.com
> >> Subject: [IronPython] weird performance issue
> >>
> >> 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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