In one embodiment, packet memory and resource memory of a memory are independently managed, with regions of packet memory being freed of packets and temporarily made available to resource memory. In one embodiment, packet memory regions are dynamically made available to resource memory so that in-service system upgrade (ISSU) of a packet switching device can be performed without having to statically allocate (as per prior systems) twice the memory space required by resource memory during normal packet processing operations. One embodiment dynamically collects fragments of packet memory stored in packet memory to form a contiguous region of memory that can be used by resource memory in a memory system that is shared between many clients in a routing complex. One embodiment assigns a contiguous region no longer used by packet memory to resource memory, and from resource memory to packet memory, dynamically without packet loss or pause.