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    SubjectRe: [Announce] [patch] Modular Scheduler Core and Completely Fair Scheduler [CFS]

    * Bill Huey <> wrote:

    > Con has been asking for module support for years if I understand your
    > patch corectly. [...]

    Yeah. Note that there are some subtle but crutial differences between
    PlugSched (which Con used, and which i opposed in the past) and this

    PlugSched cuts the interfaces at a high level in a monolithic way and
    introduces kernel/scheduler.c that uses one pluggable scheduler
    (represented via the 'scheduler' global template) at a time.

    while in this CFS patchset i'm using modularization ('scheduler
    classes') to simplify the _existing_ multi-policy implementation of the
    scheduler. These 'scheduler classes' are in a hierarchy and are stacked
    on top of each other. They are in use at once. Currently there's two of
    them: sched_ops_rt is stacked ontop of sched_ops_fair. Fortunately the
    performance impact is minimal.

    So scheduler classes are mainly a simplification of the design of the
    scheduler - not just a mere facility to select multiple schedulers.
    Their ability to also facilitate easier experimentation with schedulers
    is 'just' a happy side-effect. So all in one: it's a fairly different
    model from PlugSched (and that's why i didnt reuse PlugSched) - but
    there's indeed overlap.

    > [...] You'll also need this for -rt as well with regards to bandwidth
    > scheduling.


    scheduler classes are also useful for other purposes like containers and
    virtualization, hierarchical/group scheduling, security encapsulation,
    etc. - features that can be on-demand layered, and which we dont
    necessarily want to have enabled all the time.

    > [...] Good to see that you're moving in this direction.

    thanks! :)

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