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    SubjectRe: [PATCH] nohz1: Documentation
    On Wed, 20 Mar 2013, Paul E. McKenney wrote:

    > > > Another approach is to offload RCU callback processing to "rcuo" kthreads
    > > > using the CONFIG_RCU_NOCB_CPU=y. The specific CPUs to offload may be
    > > > selected via several methods:

    Why are there multiple rcuo threads? Would a single thread that may be
    able to run on multiple cpus not be sufficient?

    > > "Even though the SCHED_FIFO task is the only task running, because the
    > > SCHED_OTHER tasks are queued on the CPU, it currently will not enter
    > > adaptive tick mode."
    >
    > Again, good point!

    Uggh. That will cause problems and did cause problems when I tried to use
    nohz.

    The OS always has some sched other tasks around that become runnable after
    a while (like for example the vm statistics update, or the notorious slab
    scanning). As long as SCHED_FIFO is active and there is no process in the
    same scheduling class then tick needs to be off. Also wish that this would
    work with SCHED_OTHER if there is only a single task with a certain renice
    value (-10?) and the rest is runnable at lower priorities. Maybe in that
    case stop the tick for a longer period and then give the lower priority
    tasks a chance to run but then switch off the tick again.


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