Reverse mappings help the system continue to perform and scale well when large applications are placing huge memory demands on the kernel and multiple processes are sharing memory.

当大型应用程序向内核请求大量内存和多个进程共享内存时，反向映射帮助系统继续有效地运行和扩展。

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If things turn sour, positive urban trends such as declining crime and shrinking welfare rolls could sharply reverse, endangering the mayors' political fortunes and placing in jeopardy their most exciting policy proposals.

ECONOMIST: City politics