[Cython] Hudson pyregr testing takes too long

[Stefan Behnel]

Vitja Makarov, 25.04.2011 11:04:
> 2011/4/25 Stefan Behnel<stefan_ml at behnel.de>:
>> Vitja Makarov, 25.04.2011 08:19:
>>>
>>> 2011/4/25 Stefan Behnel:
>>>>
>>>> Stefan Behnel, 07.04.2011 13:52:
>>>>>
>>>>> Stefan Behnel, 07.04.2011 13:46:
>>>>>>
>>>>>> I just noticed that the CPython pyregr tests have jumped up from ~14
>>>>>> minutes for a run to ~4 hours when we added generator support.
>>>>>>
>>>>>>
>>>>>>
>>>>>> https://sage.math.washington.edu:8091/hudson/job/cython-devel-tests-pyregr-py26-c/buildTimeTrend
>>>>>>
>>>>>> I currently have no idea why that is (well, it's likely because we
>>>>>> compile
>>>>>> more tests now, but Vitja's branch ran the tests in ~30 minutes). It
>>>>>> would
>>>>>> be great if someone could find the time to analyse this problem. The
>>>>>> current run time makes it basically impossible to keep these tests
>>>>>> enabled.
>>>>>
>>>>> Ok, it looks like this is mostly an issue with the Py2.6 tests. The
>>>>> Py2.7
>>>>> tests take 30-45 minutes, which is very long, but not completely out of
>>>>> bounds. I've disabled the Py2.6 pyregr tests for now.
>>>>
>>>> There seems to be a huge memory leak which almost certainly accounts for
>>>> this. The Python process that runs the pyregr suite ends up with about
>>>> 50GB
>>>> of memory at the end, also in the latest Py3k builds.
>>>>
>>>> I have no idea where it may be, but it started to show when we merged the
>>>> generator support. That's where I noticed the instant jump in the
>>>> runtime.
>>>
>>> That's very strange for my branch it takes about 30 minutes that is ok.
>>
>> There's also a second path that's worth investigating. As part of the merge,
>> there was another change that came in: the CythonPyregrTestCase
>> implementation. This means that the regression tests are now being run
>> differently than before. The massive memory consumption may simply be due to
>> the mass of unit tests being loaded into memory.
>
>     def run_test():
> ..................................
>          try:
>              module = __import__(self.module)
>              if hasattr(module, 'test_main'):
>                  module.test_main()
>          except (unittest.SkipTest, support.ResourceDenied):
>              result.addSkip(self, 'ok')
>
>
> It seems that all the modules stay loaded so may be they should be
> unloaded with del sys.modules[module_name]?

(Binary) module unloading isn't really supported in CPython. There's PEP 
3121 that has the potential to change it, but it's not completely 
implemented, neither in CPython nor in Cython. A major problem is that 
unloading a module deletes its globals but not necessarily the code that 
uses them. For example, instances of types defined in the module can still 
be alive at that point.

The way runtests.py deals with this is forking before loading a module. 
However, this does not currently work with the "xmlrunner" which we use on 
Hudson, so we let all tests run in a single process there.

Stefan