[Twisted-Python] Twisted slow in Mac OS X fast on Windows

Jean-Paul Calderone exarkun at divmod.com
Fri Feb 20 14:19:06 EST 2009

On Fri, 20 Feb 2009 11:11:24 -0800, Brian Granger <ellisonbg.net at gmail.com> wrote:
>We use Twisted extensively in the IPython project for parallel and
>distributed computing.  We have an extensive test suite that uses
>trial to test our servers and clients.  Everything works
>great...but...the test suite takes much longer to run on OS X than
>windows.  Here is what I mean:
>1.  2.53 Ghz Intel Core 2 Duo, Mac OS X 10.5.  Test suite takes 67 seconds
>2.  *Same machine*, running Windows XP as VM in VMWare.  Test suite
>takes 17 seconds.
>I have verified that all the tests are being run on Windows.  This is
>very surprising to me as I would expect, if anything, the Windows VM
>to be a bit slower, not 3x faster.  This is the same hardware, the
>same code, the only thing that I can think of that is different is the
>reactor implementation.  I am using the default reactor on both
>* Is the Windows reactor really that fast?

Probably not.  But it depends what your test suite does.

>* Is the default (I think it is select) reactor on OS X really that slow?

Probably not.  But it depends what your test suite does.

>* Why else would it be that slow on OS X?
>* What can I do to speed this up?

The only thing that comes to mind is that some hostname lookup functions
used to be pretty slow on OS X.  I have no idea if this is still the case.
I suggest profiling the suite on OS X and Windows and comparing the results
to get a better idea of where to look for the problem.


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