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    Subjectscheduler interactivity - does this patch help?
    I've had this patch (I think from Ingo) kicking around in -mjb
    for a while. I'm going to drop it unless someone thinks it's useful
    for some testcase you have ... anyone interested?

    Thanks,

    M.

    diff -urpN -X /home/fletch/.diff.exclude 400-reiserfs_dio/kernel/sched.c 420-sched_interactive/kernel/sched.c
    --- 400-reiserfs_dio/kernel/sched.c Fri May 30 19:26:34 2003
    +++ 420-sched_interactive/kernel/sched.c Fri May 30 19:28:06 2003
    @@ -89,6 +89,8 @@ int node_threshold = 125;
    #define STARVATION_LIMIT (starvation_limit)
    #define NODE_THRESHOLD (node_threshold)

    +#define TIMESLICE_GRANULARITY (HZ/20 ?: 1)
    +
    /*
    * If a task is 'interactive' then we reinsert it in the active
    * array after it has expired its current timeslice. (it will not
    @@ -1365,6 +1367,27 @@ void scheduler_tick(int user_ticks, int
    enqueue_task(p, rq->expired);
    } else
    enqueue_task(p, rq->active);
    + } else {
    + /*
    + * Prevent a too long timeslice allowing a task to monopolize
    + * the CPU. We do this by splitting up the timeslice into
    + * smaller pieces.
    + *
    + * Note: this does not mean the task's timeslices expire or
    + * get lost in any way, they just might be preempted by
    + * another task of equal priority. (one with higher
    + * priority would have preempted this task already.) We
    + * requeue this task to the end of the list on this priority
    + * level, which is in essence a round-robin of tasks with
    + * equal priority.
    + */
    + if (!(p->time_slice % TIMESLICE_GRANULARITY) &&
    + (p->array == rq->active)) {
    + dequeue_task(p, rq->active);
    + set_tsk_need_resched(p);
    + p->prio = effective_prio(p);
    + enqueue_task(p, rq->active);
    + }
    }
    out_unlock:
    spin_unlock(&rq->lock);
    -
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