Improving hot-page detection and promotion

Tiered-memory systems feature multiple types of memory with varying performance characteristics; on such systems, good performance depends on keeping the most frequently used data in the fastest memory. Identifying that data and placing it properly is a challenge that has kept developers busy for years. Bharata Rao, presenting remotely during a memory-management-track session at the 2025 Linux Storage, Filesystem, Memory-Management, and BPF Summit, led a discussion on a potential solution he has recently posted; Raghavendra K T was also named on the session proposal. It seems likely, based on the discussion, that developers working in this area will not run out of problems anytime soon.
分级内存系统包含多种性能特性不同的内存类型；在这类系统上，实现良好的性能取决于能否将最常使用的数据保存在最快的内存中。识别这些热点数据并正确地放置它们是一项多年来让开发者不断投入的挑战。在 2025 年 Linux 存储、文件系统、内存管理与 BPF 峰会的内存管理议题上，Bharata Rao 远程发起了一场关于他近期提出的一个潜在解决方案的讨论；Raghavendra K T 也被列为会议议题提案的参与者。从讨论内容来看，该领域的开发者短时间内恐怕不会遇到“无事可做”的局面。

There are two aspects to the memory-promotion problem: detecting which pages should be moved, and actually migrating them. On the detection side, there are a number of sources for data that can be used to detect hot (frequently accessed) pages; Rao is mostly focused on approaches that involve scanning page tables to see which pages have been accessed recently. He thinks that the current scanning implementation needs an overhaul; it is tied to the NUMA-balancing code, and its operation tends to create latency spikes for applications. Since both the page-table-entry (PTE) scanning and page migration are done in process context, they interrupt user-space execution in potentially disruptive ways.
内存提升问题可分为两个