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    Subject[tip: sched/core] sched: Limit the number of task migrations per batch on RT
    The following commit has been merged into the sched/core branch of tip:

    Commit-ID: 691925f3ddccea832cf2d162dc277d2623a816e3
    Gitweb: https://git.kernel.org/tip/691925f3ddccea832cf2d162dc277d2623a816e3
    Author: Thomas Gleixner <tglx@linutronix.de>
    AuthorDate: Tue, 28 Sep 2021 14:24:25 +02:00
    Committer: Peter Zijlstra <peterz@infradead.org>
    CommitterDate: Tue, 05 Oct 2021 15:52:11 +02:00

    sched: Limit the number of task migrations per batch on RT

    Batched task migrations are a source for large latencies as they keep the
    scheduler from running while processing the migrations.

    Limit the batch size to 8 instead of 32 when running on a RT enabled
    kernel.

    Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Link: https://lkml.kernel.org/r/20210928122411.425097596@linutronix.de
    ---
    kernel/sched/core.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/kernel/sched/core.c b/kernel/sched/core.c
    index 9eaeba6..749284f 100644
    --- a/kernel/sched/core.c
    +++ b/kernel/sched/core.c
    @@ -74,7 +74,11 @@ __read_mostly int sysctl_resched_latency_warn_once = 1;
    * Number of tasks to iterate in a single balance run.
    * Limited because this is done with IRQs disabled.
    */
    +#ifdef CONFIG_PREEMPT_RT
    +const_debug unsigned int sysctl_sched_nr_migrate = 8;
    +#else
    const_debug unsigned int sysctl_sched_nr_migrate = 32;
    +#endif

    /*
    * period over which we measure -rt task CPU usage in us.
    \
     
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