Comment 6 for bug 1741954

Reviewed: https://review.openstack.org/532559
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=5ab223d1bd533e459ee61572d49aa5e159af22c4
Submitter: Zuul
Branch: stable/pike

commit 5ab223d1bd533e459ee61572d49aa5e159af22c4
Author: Armando Migliaccio <email address hidden>
Date: Mon Jan 8 22:46:04 2018 -0800

    Speed up trunk MTU enforcement check

    While things may have become generally slower for reasons still
    to be determined at the time this patch was developed, we noticed
    that enforcing MTU rules between subports and trunk parent was
    done by performing one DB lookup per subport. This patch optmizes
    the performance by piggybacking on the logic that is used to
    retrieve the subport underlying network's segmentation type when
    the segmentation type must be inherited.

    Closes-bug: #1741954

    Change-Id: Ib18427ef7a3509088eaf8fa0cfed3fb659b6baea
    (cherry picked from commit d23a9ad7313b6d4b275f3b46c89d9f79d3cfb9a4)