[Bug 1643675] Re: hugepages for non-default pagesize need manual setup

[James Page]

@jjo

Use of 'default_hugepagesz=1G' might also tweak things a bit.

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https://bugs.launchpad.net/bugs/1643675

Title:
  hugepages for non-default pagesize need manual setup

Status in libvirt package in Ubuntu:
  New
Status in systemd package in Ubuntu:
  New
Status in nova-compute package in Juju Charms Collection:
  Triaged

Bug description:
  This is a amd64 xenial/mitaka deploy using 1607 charms release
  where I need to have 1G hugepages available for openstack/kvm.

  nova-compute charm should provide ways to ease e.g.
  1G hugepages setup, currently only exposes a 
  "hugepages" setting that ends setting vm.nr_hugepages
  for the node, but even after settings kernel cmdline
  parameters for 1G hugepages (hugepagesz=1G hugepages=128),
  is not usable by libvirt-bin:

  #1 systemd:
  Installs /lib/systemd/system/dev-hugepages.mount with
  default pagesize
  => no hugetblfs mount with (e.g.) pagesize=1G

  #2 libvirt-bin:
  Installs apparmor profile ("libvirt-qemu") which only allows:
    # for access to hugepages
    owner "/run/hugepages/kvm/libvirt/qemu/**" rw,
    owner "/dev/hugepages/libvirt/qemu/**" rw,
  => not possible to have other mount points for other pagesizes.

  I've workaround'd #1,#2 above by overriding systemd's
  by creating a /etc/systemd/system/dev-hugepages.mount
  with below extra line at [Mount] section:
  Options=pagesize=1G
  -> https://paste.ubuntu.com/23513048/

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