Open Stack

Hey there,

We've talked about the slow Xenial gate during the OpenStack Summit this week and I decided to do a little digging.  I built two quick test instances: one with Trusty and the other with Xenial.

Trusty comes with python 2.7.6 and Xenial has 2.7.12.  Here are the initial comparisons:

  https://gist.github.com/major/20d7d11442685355c30d0abf0c07be98

The worst test shows that 2.7.12 on Xenial is 1.88 slower than 2.7.6 on Trusty. Wow.

I compiled 2.7.12 from source on Xenial to see if it's a packaging issue, but that didn't change anything much.  I then compiled 2.7.12 on 14.04 and found it be to be slightly slower than 2.7.6 on 14.04, but faster than 2.7.12 on 16.04.  That's confusing, so here's a ranking from fastest to slowest performance:

1) 2.7.6 on Ubuntu 14.04 (fastest)
2) 2.7.12 compiled from source on Ubuntu 14.04 (a little slower than #1)
3) 2.7.12 compiled from source on Ubuntu 16.04 (slightly faster than #4)
4) 2.7.12 on Ubuntu 16.04 (significant slower than #1)

It's evident that 2.7.12 is a little bit slower, but something in Ubuntu 16.04 makes it much worse.  I checked sysctl settings and the only big difference was the max threads per process (16.04 was about half of 14.04).  I set them both to the same value but the performance testing didn't change.

Does anyone else have any ideas of what might be causing this?

--
Major Hayden

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