I’ve been working on porting PyPI/Warehouse to using PyPy3, using the latest PyPy3 release (6.0.0) my tests on Warehouse take ~200 seconds to run, which is roughly within the realm of what I expected. I noticed when I tried to use the latest PyPy3 3.5 nightly (pypy-c-jit-95315-0a5cd8d36e99-linux64.tar.bz2) that my tests were randomly “hanging” (or taking so long to complete a single test that I got bored and filled it). It wasn’t every time, (IOW, the test it happened to would switch around each run). I thought maybe it was a problem with the functional tests, and ran only the unit tests, and it got ~19% of the way through and happened again (and in general the tests were way way slower). I went back one nightly release, to pypy-c-jit-95312-3bb86a88e1d3-linux64.tar.bz2 and tried with that, and that works as expected, with a similar runtime to PyPy3-6.0.0 and without any hangs.