add support for KSM

This adds support for KSM (kernel samepage merging). It adds a new
boolean parameter called MemoryKSM to enable the feature. The feature
can only be enabled with newer kernels.

2 files changed, 40 insertions, 0 deletions

diff --git a/man/org.freedesktop.systemd1.xml b/man/org.freedesktop.systemd1.xml
index a08108dd88..70273bbf64 100644
--- a/man/org.freedesktop.systemd1.xml
+++ b/man/org.freedesktop.systemd1.xml
@@ -3174,6 +3174,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly b ProtectHostname = ...;
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+      readonly b MemoryKSM = ...;
+      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s NetworkNamespacePath = '...';
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s IPCNamespacePath = '...';
@@ -3739,6 +3741,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
 
     <!--property ProtectHostname is not documented!-->
 
+    <!--property MemoryKSM is not documented!-->
+
     <!--property NetworkNamespacePath is not documented!-->
 
     <!--property IPCNamespacePath is not documented!-->
@@ -4405,6 +4409,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2eservice {
 
     <variablelist class="dbus-property" generated="True" extra-ref="ProtectHostname"/>
 
+    <variablelist class="dbus-property" generated="True" extra-ref="MemoryKSM"/>
+
     <variablelist class="dbus-property" generated="True" extra-ref="NetworkNamespacePath"/>
 
     <variablelist class="dbus-property" generated="True" extra-ref="IPCNamespacePath"/>
@@ -5184,6 +5190,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly b ProtectHostname = ...;
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+      readonly b MemoryKSM = ...;
+      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s NetworkNamespacePath = '...';
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s IPCNamespacePath = '...';
@@ -5761,6 +5769,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
 
     <!--property ProtectHostname is not documented!-->
 
+    <!--property MemoryKSM is not documented!-->
+
     <!--property NetworkNamespacePath is not documented!-->
 
     <!--property IPCNamespacePath is not documented!-->
@@ -6407,6 +6417,8 @@ node /org/freedesktop/systemd1/unit/avahi_2ddaemon_2esocket {
 
     <variablelist class="dbus-property" generated="True" extra-ref="ProtectHostname"/>
 
+    <variablelist class="dbus-property" generated="True" extra-ref="MemoryKSM"/>
+
     <variablelist class="dbus-property" generated="True" extra-ref="NetworkNamespacePath"/>
 
     <variablelist class="dbus-property" generated="True" extra-ref="IPCNamespacePath"/>
@@ -7061,6 +7073,8 @@ node /org/freedesktop/systemd1/unit/home_2emount {
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly b ProtectHostname = ...;
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+      readonly b MemoryKSM = ...;
+      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s NetworkNamespacePath = '...';
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s IPCNamespacePath = '...';
@@ -7566,6 +7580,8 @@ node /org/freedesktop/systemd1/unit/home_2emount {
 
     <!--property ProtectHostname is not documented!-->
 
+    <!--property MemoryKSM is not documented!-->
+
     <!--property NetworkNamespacePath is not documented!-->
 
     <!--property IPCNamespacePath is not documented!-->
@@ -8130,6 +8146,8 @@ node /org/freedesktop/systemd1/unit/home_2emount {
 
     <variablelist class="dbus-property" generated="True" extra-ref="ProtectHostname"/>
 
+    <variablelist class="dbus-property" generated="True" extra-ref="MemoryKSM"/>
+
     <variablelist class="dbus-property" generated="True" extra-ref="NetworkNamespacePath"/>
 
     <variablelist class="dbus-property" generated="True" extra-ref="IPCNamespacePath"/>
@@ -8911,6 +8929,8 @@ node /org/freedesktop/systemd1/unit/dev_2dsda3_2eswap {
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly b ProtectHostname = ...;
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
+      readonly b MemoryKSM = ...;
+      @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s NetworkNamespacePath = '...';
       @org.freedesktop.DBus.Property.EmitsChangedSignal("const")
       readonly s IPCNamespacePath = '...';
@@ -9402,6 +9422,8 @@ node /org/freedesktop/systemd1/unit/dev_2dsda3_2eswap {
 
     <!--property ProtectHostname is not documented!-->
 
+    <!--property MemoryKSM is not documented!-->
+
     <!--property NetworkNamespacePath is not documented!-->
 
     <!--property IPCNamespacePath is not documented!-->
@@ -9952,6 +9974,8 @@ node /org/freedesktop/systemd1/unit/dev_2dsda3_2eswap {
 
     <variablelist class="dbus-property" generated="True" extra-ref="ProtectHostname"/>
 
+    <variablelist class="dbus-property" generated="True" extra-ref="MemoryKSM"/>
+
     <variablelist class="dbus-property" generated="True" extra-ref="NetworkNamespacePath"/>
 
     <variablelist class="dbus-property" generated="True" extra-ref="IPCNamespacePath"/>
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml
index 3f3ed77f46..9fb6c9b908 100644
--- a/man/systemd.exec.xml
+++ b/man/systemd.exec.xml
@@ -1774,6 +1774,22 @@ BindReadOnlyPaths=/var/lib/systemd</programlisting>
       </varlistentry>
 
       <varlistentry>
+        <term><varname>MemoryKSM=</varname></term>
+
+        <listitem><para>Takes a boolean argument. When set, it enables KSM (kernel samepage merging) for
+        the processes. KSM is a memory-saving de-duplication feature. Anonymous memory pages with identical
+        content can be replaced by a single write-protected page. This feature should only be enabled for
+        jobs that share the same security domain. For details, see
+        <ulink url="https://docs.kernel.org/admin-guide/mm/ksm.html">Kernel Samepage Merging</ulink> in the
+        kernel documentation.</para>
+
+        <para>Note that this functionality might not be available, for example if KSM is disabled in the
+        kernel, or the kernel doesn't support controlling KSM at the process level through
+        <function>prctl()</function>.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
         <term><varname>PrivateUsers=</varname></term>
 
         <listitem><para>Takes a boolean argument. If true, sets up a new user namespace for the executed processes and