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    SubjectRe: [RFC v3 PATCH 0/5] mm: memcontrol: do memory reclaim when offlining
    On Wed, Jan 09, 2019 at 12:36:11PM -0800, Yang Shi wrote:
    > As I mentioned above, if we know some page caches from some memcgs
    > are referenced one-off and unlikely shared, why just keep them
    > around to increase memory pressure?

    It's just not clear to me that your scenarios are generic enough to
    justify adding two interfaces that we have to maintain forever, and
    that they couldn't be solved with existing mechanisms.

    Please explain:

    - Unmapped clean page cache isn't expensive to reclaim, certainly
    cheaper than the IO involved in new application startup. How could
    recycling clean cache be a prohibitive part of workload warmup?

    - Why you cannot temporarily raise the kswapd watermarks right before
    an important application starts up (your answer was sorta handwavy)

    - Why you cannot use madvise/fadvise when an application whose cache
    you won't reuse exits

    - Why you couldn't set memory.high or memory.max to 0 after the
    application quits and before you call rmdir on the cgroup

    Adding a permanent kernel interface is a serious measure. I think you
    need to make a much better case for it, discuss why other options are
    not practical, and show that this will be a generally useful thing for
    cgroup users and not just a niche fix for very specific situations.

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