---
prelude: >
    In order to reduce the time spent processing security group updates in
    the L2 agent, conntrack deletion is now performed in a set of worker
    threads instead of the main agent thread, so it can return to processing
    other events quickly.
upgrade:
  - |
    On an upgrade, conntrack entries will now be cleaned-up in a worker
    thread, instead of in the calling thread.
fixes:
  - |
    Fixes bug `1745468 <https://bugs.launchpad.net/neutron/+bug/1745468>`_.