一句话：提出 Mosaic 页，将多个离散翻译压缩进单个 TLB 项，不依赖物理连续性即可提升 TLB 覆盖范围。
TLB 正成为大数据应用的瓶颈：条目数受延迟限制，增长远慢于工作集。已有方案如大页、穿孔页或 TLB 合并依赖物理连续性，而内存碎片整理成本可能抵消收益。Mosaic 页利用虚拟连续性捕获局部性，但不要求物理连续；它借助哈希理论约束内存映射，实现物理地址压缩，同时不降低内存利用率或增加换页。作者在 gem5 和修改版 Linux 中实现全系统原型，并对关键路径哈希函数做 Verilog 时序与面积分析。在多种负载中，Mosaic 将 TLB miss 减少 6-81%；内存映射约束在内存 98% 满前未引发冲突，超配时多数情况换页少于 Linux；28nm CMOS 下哈希电路最高 4 GHz，表明 Mosaic TLB 不太影响时钟频率。
The TLB is increasingly a bottleneck for big data applications. In most designs, the number of TLB entries are highly constrained by latency requirements, and growing much more slowly than the working sets of applications. Many solutions to this problem, such as huge pages, perforated pages, or TLB coalescing, rely on physical contiguity for performance gains, yet the cost of defragmenting memory can easily nullify these gains. This paper introduces mosaic pages, which increase TLB reach by compressing multiple, discrete translations into one TLB entry. Mosaic leverages virtual contiguity for locality, but does not use physical contiguity. Mosaic relies on recent advances in hashing theory to constrain memory mappings, in order to realize this physical address compression without reducing memory utilization or increasing swapping. This paper presents a full-system prototype of Mosaic, in gem5 and modified Linux. In simulation and with comparable hardware to a traditional design, mosaic reduces TLB misses in several workloads by 6-81%. Our results show that Mosaic’s constraints on memory mappings do not harm performance, we never see conflicts before memory is 98% full in our experiments — at which point, a traditional design would also likely swap. Once memory is over-committed, Mosaic swaps fewer pages than Linux in most cases. Finally, we present timing and area analysis for a verilog implementation of the hashing function required on the critical path for the TLB, and show that on a commercial 28nm CMOS process; the circuit runs at a maximum frequency of 4 GHz, indicating that a mosaic TLB is unlikely to affect clock frequency.
@inproceedings{paperbot10069,
title = {Mosaic Pages: Big TLB Reach with Small Pages},
author = {Krishnan Gosakan and Jaehyun Han and William Kuszmaul and Ibrahim N. Mubarek and Nirjhar Mukherjee and Karthik Sriram and Guido Tagliavini and Evan West and Michael A. Bender and Abhishek Bhattacharjee and Alex Conway and Martin Farach-Colton and Jayneel Gandhi and Rob Johnson and Sudarsun Kannan and Donald E. Porter},
booktitle = {ASPLOS},
year = {2023},
doi = {10.1145/3582016.3582021}
}