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    Subject[RFC][PATCH 0/4] Memory controller soft limit patches

    Here is v1 of the new soft limit implementation. Soft limits is a new feature
    for the memory resource controller, something similar has existed in the
    group scheduler in the form of shares. We'll compare shares and soft limits
    below. I've had soft limit implementations earlier, but I've discarded those
    approaches in favour of this one.

    Soft limits are the most useful feature to have for environments where
    the administrator wants to overcommit the system, such that only on memory
    contention do the limits become active. The current soft limits implementation
    provides a soft_limit_in_bytes interface for the memory controller and not
    for memory+swap controller. The implementation maintains an RB-Tree of groups
    that exceed their soft limit and starts reclaiming from the group that
    exceeds this limit by the maximum amount.

    This is an RFC implementation and is not meant for inclusion

    TODOs

    1. The shares interface is not yet implemented, the current soft limit
    implementation is not yet hierarchy aware. The end goal is to add
    a shares interface on top of soft limits and to maintain shares in
    a manner similar to the group scheduler
    2. The current implementation maintains the delta from the soft limit
    and pushes back groups to their soft limits, a ratio of delta/soft_limit
    is more useful
    3. It would be nice to have more targetted reclaim (in terms of pages to
    recalim) interface. So that groups are pushed back, close to their soft
    limits.

    Tests
    -----

    I've run two memory intensive workloads with differing soft limits and
    seen that they are pushed back to their soft limit on contention. Their usage
    was their soft limit plus additional memory that they were able to grab
    on the system.

    Please review, comment.

    Series
    ------

    memcg-soft-limit-documentation.patch
    memcg-add-soft-limit-interface.patch
    memcg-organize-over-soft-limit-groups.patch
    memcg-soft-limit-reclaim-on-contention.patch

    --
    Balbir


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