From 7e585445b90f3a2bdab033f0e8ca6da4cb56318f Mon Sep 17 00:00:00 2001
From: "Dustin C. Hatch" <dustin@hatch.name>
Date: Fri, 22 Mar 2019 09:25:48 -0500
Subject: [PATCH] roles/vmhost: Enable KSM

This commit adds a systemd unit to enable the Kernel Same-page Merging
daemon on VM hosts. This allows much greater virtual machine density,
especially when many VMs are running the same guest OS.
---
 roles/vmhost/files/ksm.service | 12 ++++++++++++
 roles/vmhost/tasks/main.yml    | 15 +++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 roles/vmhost/files/ksm.service

diff --git a/roles/vmhost/files/ksm.service b/roles/vmhost/files/ksm.service
new file mode 100644
index 0000000..aeb77c9
--- /dev/null
+++ b/roles/vmhost/files/ksm.service
@@ -0,0 +1,12 @@
+# vim: set ft=dosini :
+[Unit]
+Description=Kernel Same-Page Merging
+
+[Service]
+Type=oneshot
+RemainAfterExit=yes
+ExecStart=/bin/sh -c "echo 1 > /sys/kernel/mm/ksm/run"
+ExecStop=/bin/sh -c "echo 0 > /sys/kernel/mm/ksm/run"
+
+[Install]
+WantedBy=multi-user.target
diff --git a/roles/vmhost/tasks/main.yml b/roles/vmhost/tasks/main.yml
index 310c052..59e5af2 100644
--- a/roles/vmhost/tasks/main.yml
+++ b/roles/vmhost/tasks/main.yml
@@ -69,3 +69,18 @@
     immediate=yes
     state=enabled
   notify: save firewalld configuration
+
+- name: ensure systemd ksm unit is installed
+  copy:
+    src=ksm.service
+    dest=/etc/systemd/system/ksm.service
+    mode=0644
+  notify: reload systemd
+- name: ensure systemd ksm unit starts at boot
+  service:
+    name=ksm
+    enabled=yes
+- name: ensure systemd ksm unit is running
+  service:
+    name=ksm
+    state=started