Comment 0 for bug 1638695

I work on the OpenStack-Ansible project and we've noticed that testing jobs on 16.04 take quite a bit longer to complete than on 14.04. They complete within an hour on 14.04 but they normally take 90 minutes or more on 16.04. We use the same version of Ansible with both versions of Ubuntu.

After more digging, I tested python performance (using the 'performance' module) on 14.04 (2.7.6) and on 16.04 (2.7.12). There is a significant performance difference between each version of python. That is detailed in a spreadsheet[0].

I began using perf to dig into the differences when running the python performance module and when using Ansible playbooks. CPU migrations (as measured by perf) are doubled in Ubuntu 16.04 when running the same python workloads.

I tried changing some of the kerne.sched sysctl configurables but they had very little effect on the results.

I compiled python 2.7.12 from source on 14.04 and found the performance to be unchanged there. I'm not entirely sure where the problem might be now.

We also have a bug open in OpenStack-Ansible[1] that provides additional detail. Thanks in advance for any help you can provide!

[0] https://docs.google.com/spreadsheets/d/18MmptS_DAd1YP3OhHWQqLYVA9spC3xLt4PS3STI6tds/edit?usp=sharing
[1] https://bugs.launchpad.net/openstack-ansible/+bug/1637494