Comment 13 for bug 1780348

Reviewed: https://review.openstack.org/639984
Committed: https://git.openstack.org/cgit/openstack/charm-nova-compute/commit/?id=c9a19c40777ea40d64c22070c1346c14708fabdf
Submitter: Zuul
Branch: master

commit c9a19c40777ea40d64c22070c1346c14708fabdf
Author: Pete Vander Giessen <email address hidden>
Date: Wed Feb 27 15:50:05 2019 +0100

    Added gc_threshold overrides to sysctl.conf

    When clouds have a large number of hosts, the default size of the ARP
    cache is too small. The cache can overflow, which means that the
    system has no way to reach some ip addresses.

    Setting the threshold limits higher addresses the situation, in a
    reasonably safe way (the maximum impact is 5MB or so of additional RAM
    used). Docs on ARP at http://man7.org/linux/man-pages/man7/arp.7.html,
    and more discussion of the issue in the bug.

    Change-Id: Iaf8382ee0b42e1444cfea589bb05a687cd0c23fa
    Closes-Bug: 1780348