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    SubjectRe: RT task scheduling
    On Wed, Apr 05, 2006 at 08:25:04PM -0700, Darren Hart wrote:
    > Part of the issue here is to define what we consider "correct behavior" for
    > SCHED_FIFO realtime tasks. Do we (A) need to strive for "strict realtime
    > priority scheduling" where the NR_CPUS highest priority runnable SCHED_FIFO
    > tasks are _always_ running? Or do we (B) take the best effort approach with
    > an upper limit RT priority imbalances, where an imbalance may occur (say at
    > wakeup or exit) but will be remedied within 1 tick. The smpnice patches
    > improve load balancing, but don't provide (A).

    I regret getting into this discussion late, but it should always be (A)
    if you're building a kernel for strict RT usage. (B) is for a system that's
    more general purpose. It's not a "one policy fits all" kind of problem.

    The search costs of (A) could be be significant and may degrade system
    performance. Optimizations for that case is for another discussion.


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