diff --git a/controller_manager/doc/userdoc.rst b/controller_manager/doc/userdoc.rst
index 5a86c3373b..ea8fa75544 100644
--- a/controller_manager/doc/userdoc.rst
+++ b/controller_manager/doc/userdoc.rst
@@ -341,7 +341,7 @@ The controller_manager can be launched with the ros2_control_node executable. Th
 
 The ros2_control_node executable uses the following parameters from the ``controller_manager`` node:
 
-lock_memory (optional; bool; default: false)
+lock_memory (optional; bool; default: false for a non-realtime kernel, true for a realtime kernel)
   Locks the memory of the ``controller_manager`` node at startup to physical RAM in order to avoid page faults
   and to prevent the node from being swapped out to disk.
   Find more information about the setup for memory locking in the following link : `How to set ulimit values <https://access.redhat.com/solutions/61334>`_
diff --git a/controller_manager/src/ros2_control_node.cpp b/controller_manager/src/ros2_control_node.cpp
index 5dace36d34..af4f5e50a3 100644
--- a/controller_manager/src/ros2_control_node.cpp
+++ b/controller_manager/src/ros2_control_node.cpp
@@ -59,7 +59,8 @@ int main(int argc, char ** argv)
 
   const bool use_sim_time = cm->get_parameter_or("use_sim_time", false);
 
-  const bool lock_memory = cm->get_parameter_or<bool>("lock_memory", false);
+  const bool has_realtime = realtime_tools::has_realtime_kernel();
+  const bool lock_memory = cm->get_parameter_or<bool>("lock_memory", has_realtime);
   std::string message;
   if (lock_memory && !realtime_tools::lock_memory(message))
   {