diff --git a/stack.sh b/stack.sh
index 20cdc1dfcc..504d94f148 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1006,6 +1006,22 @@ init_service_check
 # 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
 # ==============
diff --git a/stackrc b/stackrc
index 61501b5696..b53f791380 100644
--- a/stackrc
+++ b/stackrc
@@ -104,6 +104,14 @@ if [[ "$USE_SYSTEMD" == "True" ]]; then
     USE_SCREEN=False
 fi
 
+# Whether or not to enable Kernel Samepage Merging (KSM) if available.
+# This allows programs that mark their memory as mergeable to share
+# memory pages if they are identical. This is particularly useful with
+# libvirt backends. This reduces memory useage at the cost of CPU overhead
+# to scan memory. We default to enabling it because we tend to be more
+# memory constrained than CPU bound.
+ENABLE_KSM=$(trueorfalse True ENABLE_KSM)
+
 # When using screen, should we keep a log file on disk?  You might
 # want this False if you have a long-running setup where verbose logs
 # can fill-up the host.