Improved techniques are disclosed for performing an in-service upgrade of software associated with a network or packet processor. By way of example, a method of managing data structures associated with code executable on a packet processor includes the following steps. Data structures in the code are identified as being one of static data structures and non-static data structures, wherein a static data structure includes a data structure that is not changed during execution of the packet processor code and a non-static data structure includes a data structure that is changed during execution of the packet processor code. One or more data structures associated with the packet processor code are managed in a manner specific to the identification of the one or more data structures as static data structures or non-static data structures. At least a portion of the data structures may include tree structures.