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    SubjectRe: [RFC v3 PATCH 0/5] mm: zap pages with read mmap_sem in munmap for large mapping
    On Sat 30-06-18 06:39:40, Yang Shi wrote:
    >
    > Background:
    > Recently, when we ran some vm scalability tests on machines with large memory,
    > we ran into a couple of mmap_sem scalability issues when unmapping large memory
    > space, please refer to https://lkml.org/lkml/2017/12/14/733 and
    > https://lkml.org/lkml/2018/2/20/576.
    >
    >
    > History:
    > Then akpm suggested to unmap large mapping section by section and drop mmap_sem
    > at a time to mitigate it (see https://lkml.org/lkml/2018/3/6/784).
    >
    > V1 patch series was submitted to the mailing list per Andrew’s suggestion
    > (see https://lkml.org/lkml/2018/3/20/786). Then I received a lot great feedback
    > and suggestions.
    >
    > Then this topic was discussed on LSFMM summit 2018. In the summit, Michal Hock
    > suggested (also in the v1 patches review) to try "two phases" approach. Zapping
    > pages with read mmap_sem, then doing via cleanup with write mmap_sem (for
    > discussion detail, see https://lwn.net/Articles/753269/)

    The cover letter should really describe your approach to the problem.
    But there is none here.
    --
    Michal Hocko
    SUSE Labs

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