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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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