[openstack-dev] [trove] timeouts in gate-trove-python34-db

Victor Stinner vstinner at redhat.com
Mon May 16 14:56:40 UTC 2016

Le 16/05/2016 16:12, Peter Stachowski a écrit :
> Amrith is right though - python34 is *much* slower running this check
> (and somewhat in general) than python27.  Maybe that doesn't
> translate into real-world performance data, but it has made me a bit
> nervous nonetheless.

IMHO we should look more closely to the output. See my comments on the 
bug report:


Currently, running unit tests on Python 3 runs 686 tests in 15.971s, 
whereas Python 2 runs 1495 tests in 22.595s. Python 3 is "faster" :-) 
(16 sec < 23 sec)

The whole Python 3 job takes 10 minutes, but in these 10 minutes, almost 
8 minutes are taken just to build binary wheel packages. On Python 2, 
prebuilt packages are used and so creating the virtual environment is 
much faster (around one minute). I proposed a change to prebuild also 
wheel packages on Python 3:


Ok, but sometimes we get timeout, right? Again, if you look closely to 
the output, between two runs on Python 2, the timing also changes a lot:

(a) Ran 1495 tests in 22.595s
(b) Ran 1495 tests in 393.364s => 17x slower!

The issue is not specific to Python 3. But it looks like the random 
slowdown is much larger on Python 3. Duration of Python 3 unit tests:

(a) "Ran 686 tests in 15.971s"
(b) "Ran 686 tests in 1581.090s" => 100x slower!

I guess that the difference is that Python 3 unit tests are currently 
run sequentially (1 process), whereas Python 2 unit tests are run in 
parallel (8 processes).

*Again* please check the code detecting dangling mocks. For example, 
"tox -e py34" takes 14 seconds without this code, 177 seconds with the 
code: 12x slower with the code.


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