diff --git a/stack.sh b/stack.sh
index 20cdc1d..504d94f 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1006,6 +1006,22 @@
 # Save configuration values
 save_stackenv $LINENO
 
+# Kernel Samepage Merging (KSM)
+# -----------------------------
+
+# Processes that mark their memory as mergeable can share identical memory
+# pages if KSM is enabled. This is particularly useful for nova + libvirt
+# backends but any other setup that marks its memory as mergeable can take
+# advantage. The drawback is there is higher cpu load; however, we tend to
+# be memory bound not cpu bound so enable KSM by default but allow people
+# to opt out if the CPU time is more important to them.
+
+if [[ "ENABLE_KSM" == "True" ]] ; then
+    if [[ -f /sys/kernel/mm/ksm/run ]] ; then
+        sudo sh -c "echo 1 > /sys/kernel/mm/ksm/run"
+    fi
+fi
+
 
 # Start Services
 # ==============