Tidying Up the Address Space
Vinay Banakar, Suli Yang, Kan Wu, Andrea Carol Arpaci-Dusseau, Remzi H. Arpaci-Dusseau, Kimberly Keeton · 2025
Memory tiering in datacenters does not achieve its full potential due to hotness fragmentation---the intermingling of hot and cold objects within memory pages. This fragmentation prevents page-basedreclamation systems from distinguishing truly hot pages frompages containing mostly cold objects, fundamentally limiting memory efficiency despite highly skewed accesses. We introduce address-space engineering: dynamically reorganizing application virtual address spaces to create uniformly hot and cold regions that any page-level tiering backend can manage effectively. HADES demonstrates this frontend/backend approach through a compiler-runtime system that tracks and migrates objects based on access patterns, requiring minimal developer intervention. Evaluations across ten data structures achieve up to 70% memory reduction with 3% performance overhead, showing that address space engineering enables existing reclamation systems to reclaim memory aggressively without performance degradation.