Leadership supercomputers feature a diversity of storage, from node-local persistent memory and NVMe SSDs to network-interconnected ash memory and HDD. Memory mapping les on dierent tiers of storage provides a uniform interface in applications. However, system-wide services like mmap are optimized for generality and lack exibility for enabling application-specic optimizations. In this work, we present UMap to enable user-space page management that can be easily adapted to access patterns in applications and storage characteristics. UMap uses the userfaultfd mechanism to handle page faults in multi-threaded applications eciently. By providing a data object abstraction layer, UMap is extensible to support various backing stores. The design of UMap supports dynamic load balancing and I/O decoupling for scalable performance. UMap also uses application hints to improve the selection of caching, prefetching, and eviction policies. We evaluate UMap in ve benchmarks and real applications on two systems. Our results show that leveraging application knowledge for page management could substantially improve performance. On average, UMap achieved 1.25 to 2.5 times improvement using the adapted congurations compared to the system service.