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    Subject[RFC 0/5] sched: Add CPU rate caps
    These patches implement CPU usage rate limits for tasks.

    Although the rlimit mechanism already has a CPU usage limit (RLIMIT_CPU)
    it is a total usage limit and therefore (to my mind) not very useful.
    These patches provide an alternative whereby the (recent) average CPU
    usage rate of a task can be limited to a (per task) specified proportion
    of a single CPU's capacity. The limits are specified in parts per
    thousand and come in two varieties -- hard and soft. The difference
    between the two is that the system tries to enforce hard caps regardless
    of the other demand for CPU resources but allows soft caps to be
    exceeded if there are spare CPU resources available. By default, tasks
    will have both caps set to 1000 (i.e. no limit) but newly forked tasks
    will inherit any caps that have been imposed on their parent from the
    parent. The mimimim soft cap allowed is 0 (which effectively puts the
    task in the background) and the minimim hard cap allowed is 1.

    Care has been taken to minimize the overhead inflicted on tasks that
    have no caps and my tests using kernbench indicate that it is hidden in
    the noise.


    The first patch in this series fixes some problems with priority
    inheritance that are present in 2.6.17-rc4-mm3 but will be fixed in
    the next -mm kernel.

    Signed-off-by: Peter Williams <>

    Peter Williams

    "Learning, n. The kind of ignorance distinguishing the studious."
    -- Ambrose Bierce
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