Gemina: A Coordinated and High-Performance Memory Deduplication Engine

Memory deduplication is widely used to effectively reduce the memory footprint in operating systems, while huge pages are employed to enhance access performance by increasing TLB hit rates. Unfortunately, duplicate huge pages are very rare in memory, leading to most huge pages being split into base pages during deduplication, which degrades access performance by up to $\mathbf{4 3 \%}$. Although asynchronous huge page promotion attempts to elevate multiple base pages to huge pages to maximize performance, deduplication disrupts the uniformity of page attributes, limiting the effectiveness of such promotions. To address this problem, we designed Gemina, a new memory deduplication scheme that coordinates huge page management. Gemina employs a fine-grained detector to distinguish pages, redundancy and hotness, a distributor to process pages conservatively and avoid frequent switches, and an adapter to organize memory for fast conversion. This approach balances the trade-off between performance and space efficiency in memory management. Experimental evaluations show that, compared to the naive KSM-based deduplication scheme, Gemina can achieve $96.1 \%$ of the memory savings of KSM while also improving memory access performance by $\mathbf{4 3. 1 \%}$ in random access.