[IronPython] Question about Control.Invoke and CallTargets

Glenn Jones glenn.k.jones+ipy at gmail.com
Tue Nov 25 16:47:01 CET 2008

Hello guys,

We're seeing some strange behaviour when doing cross-thread invoking in
Resolver. Unfortunately, we can't get a minimal repro for this, so I'll just
describe what's going on and hopefully something will be obvious.

We do our recalcs in a background thread, to avoid blocking the GUI. When a
recalc finishes, it has to update the UI with the results of the
calculations. We do that with:

    form.Invoke(self._synchroniseUI.Target, self, startedTime, aborted,

where 'form' is our main form, 'self' is a Document instance that holds the
sub-engine and all the results, `startedTime` is a DateTime, `aborted` is a
ManualResetEvent, and `state` is an object with some state extracted from
the recalculations.

We have instrumented the execution of this, and we find this weird pattern:
While _synchroniseUI takes say 500ms, form.Invoke takes 5000ms, but only the
first time it's called. Subsequent updates behave normally. Our guess would
be that some kind of overhead is created lazily once, and comes for free
after that, but it's hard to see what's going on.

We've tried the same Invoke call with CallTarget0 and a lambda with the
arguments and with CallTarget5 with the same results.

Is there something potentially expensive that involves CallTargets and
cross-thread invocations? This was fine in IronPython 1.1.

Glenn & Orestis
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.python.org/pipermail/ironpython-users/attachments/20081125/e9e45a8f/attachment.html>

More information about the Ironpython-users mailing list