The conventional virtual-to-physical address mapping scheme enables a virtual address to flexibly map to any physical address. This flexibility necessitates large data structures to store virtual-to-physical mappings, which incurs significantly high address translation latency and translation-induced interference in the memory hierarchy, especially in data-intensive workloads. Restricting the address mapping so that a virtual address can map to only a specific set of physical addresses can significantly reduce the overheads associated with the conventional address translation by making use of compact and more efficient translation structures. However, restricting the address mapping flexibility across the entire main memory severely limits data sharing across different processes and increases memory under-utilization. In this work, we propose Utopia, a new hybrid virtual-to-physical address mapping scheme that allows both flexible and restrictive hash-based address mapping schemes to co-exist in a system. The key idea of Utopia is to manage the physical memory using two types of physical memory segments: restrictive segments and flexible segments. A restrictive segment uses a restrictive, hash-based address mapping scheme to map the virtual addresses to only a specific set of physical addresses and enable faster address translation using compact and efficient translation structures. A flexible segment is similar to the conventional address mapping scheme and provides full virtual-to-physical address mapping flexibility. By mapping data to a restrictive segment, Utopia enables faster address translation with lower translation-induced interference whenever a flexible address mapping is not necessary. Our evaluation using 11 data-intensive workloads shows that Utopia improves performance by 24% on average in single-core workloads over the baseline four-level radix-tree page table design.

翻译：传统虚拟-物理地址映射方案允许虚拟地址灵活映射到任意物理地址。这种灵活性需要存储虚拟-物理映射的大型数据结构，导致地址转换延迟显著增加，并在内存层次结构中引发由转换导致的干扰，尤其在数据密集型工作负载中。若限制地址映射，使虚拟地址仅能映射到特定物理地址集，则可利用紧凑且高效的转换结构显著降低传统地址转换的开销。然而，在整个主存中限制地址映射的灵活性会严重限制跨进程数据共享，并加剧内存利用率不足。本研究提出Utopia——一种新型混合虚拟-物理地址映射方案，该方案允许系统中同时存在灵活与限制性基于哈希的地址映射方法。Utopia的核心思想是通过两种物理内存段管理物理内存：限制段与灵活段。限制段采用限制性基于哈希的地址映射，将虚拟地址仅映射到特定物理地址集，并通过紧凑高效的转换结构实现更快的地址转换；灵活段则类似传统地址映射方案，提供完整的虚拟-物理地址映射灵活性。当无需灵活地址映射时，Utopia通过将数据映射至限制段，可降低转换引发的干扰，实现更快速的地址转换。基于11项数据密集型工作负载的评估表明，与基线四级基数树页表设计相比，Utopia在单核工作负载中平均性能提升24%。