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    SubjectRe: [PATCH] mm: mlock: remove lru_add_drain_all()
    On Wed, 18 Oct 2017 16:17:30 -0700
    Shakeel Butt <shakeelb@google.com> wrote:

    > Recently we have observed high latency in mlock() in our generic
    > library and noticed that users have started using tmpfs files even
    > without swap and the latency was due to expensive remote LRU cache
    > draining.
    >
    > Is lru_add_drain_all() required by mlock()? The answer is no and the
    > reason it is still in mlock() is to rapidly move mlocked pages to
    > unevictable LRU. Without lru_add_drain_all() the mlocked pages which
    > were on pagevec at mlock() time will be moved to evictable LRUs but
    > will eventually be moved back to unevictable LRU by reclaim. So, we
    > can safely remove lru_add_drain_all() from mlock(). Also there is no
    > need for local lru_add_drain() as it will be called deep inside
    > __mm_populate() (in follow_page_pte()).
    >
    > Signed-off-by: Shakeel Butt <shakeelb@google.com>
    > ---

    Does this perturb statistics around LRU pages in cgroups and meminfo
    about where the pages actually belong?

    Balbir Singh.

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