Adds basic host kernel optimisation

This change adds three values to basic kernel optimisation which
should result in a more stable system.

Values that will be added in:
  - { key: 'vm.dirty_background_ratio', value: 5 }
  - { key: 'vm.dirty_ratio', value: 10 }
  - { key: 'vm.swappiness', value: 5 }

These values should improve general system operation and performance
when hosts have a potential for high IO. This is especially true in
a containerized environment when there are more than 20+ containers
running on a single host all potentially using LVM as the backend.

Change-Id: Ie4bf8d4d7e1b77c12bb3abec1b2d75c47ed29895
Closes-Bug: 1409755

rpc_deployment/inventory/group_vars/all.yml

@@ -80,6 +80,11 @@ host_kernel_modules:
   - dm_multipath
   - dm_snapshot
 
+host_kernel_tuning:
+  - { key: 'vm.dirty_background_ratio', value: 5 }
+  - { key: 'vm.dirty_ratio', value: 10 }
+  - { key: 'vm.swappiness', value: 10 }
+
 
 ## Base Packages
 apt_common_packages:

rpc_deployment/roles/host_common/tasks/main.yml

@@ -20,6 +20,16 @@
 - include: irqbalance.yml
 - include: check_container_bridge.yml
 
+- name: Set basic kernel optimization
+  sysctl:
+    name: "{{ item.key }}"
+    value: "{{ item.value }}"
+    sysctl_set: "{{ item.set|default('yes') }}"
+    state: "{{ item.state|default('present') }}"
+    reload: "{{ item.reload|default('yes') }}"
+  with_items: host_kernel_tuning
+  when: host_kernel_tuning is defined
+
 - name: Create /openstack hierachy
   file:
     path: "{{item}}"