Can you try the following patch and see if it helps. There's also one minor
preemption logic fix in there that I'm planning on including. Thanks!
---
kernel/sched.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
Index: linux-2.6.21-rc3-mm2/kernel/sched.c
===================================================================
--- linux-2.6.21-rc3-mm2.orig/kernel/sched.c 2007-03-12 08:47:43.000000000 +1100
+++ linux-2.6.21-rc3-mm2/kernel/sched.c 2007-03-12 09:10:33.000000000 +1100
@@ -96,10 +96,9 @@ unsigned long long __attribute__((weak))
* provided it is not a realtime comparison.
*/
#define TASK_PREEMPTS_CURR(p, curr) \
- (((p)->prio < (curr)->prio) || (((p)->prio == (curr)->prio) && \
+ (((p)->prio < (curr)->prio) || (!rt_task(p) && \
((p)->static_prio < (curr)->static_prio && \
- ((curr)->static_prio > (curr)->prio)) && \
- !rt_task(p)))
+ ((curr)->static_prio > (curr)->prio))))
/*
* This is the time all tasks within the same priority round robin.
@@ -3323,7 +3322,7 @@ static inline void major_prio_rotation(s
*/
static inline void rotate_runqueue_priority(struct rq *rq)
{
- int new_prio_level, remaining_quota;
+ int new_prio_level;
struct prio_array *array;
/*
@@ -3334,7 +3333,6 @@ static inline void rotate_runqueue_prior
if (unlikely(sched_find_first_bit(rq->dyn_bitmap) < rq->prio_level))
return;
- remaining_quota = rq_quota(rq, rq->prio_level);
array = rq->active;
if (rq->prio_level > MAX_PRIO - 2) {
/* Major rotation required */
@@ -3368,10 +3366,11 @@ static inline void rotate_runqueue_prior
}
rq->prio_level = new_prio_level;
/*
- * While we usually rotate with the rq quota being 0, it is possible
- * to be negative so we subtract any deficit from the new level.
+ * As we are merging to a prio_level that may not have anything in
+ * its quota we add 1 to ensure the tasks get to run in schedule() to
+ * add their quota to it.
*/
- rq_quota(rq, new_prio_level) += remaining_quota;
+ rq_quota(rq, new_prio_level) += 1;
}
static void task_running_tick(struct rq *rq, struct task_struct *p)
@@ -3397,12 +3396,11 @@ static void task_running_tick(struct rq
if (!--p->time_slice)
task_expired_entitlement(rq, p);
/*
- * The rq quota can become negative due to a task being queued in
- * scheduler without any quota left at that priority level. It is
- * cheaper to allow it to run till this scheduler tick and then
- * subtract it from the quota of the merged queues.
+ * We only employ the deadline mechanism if we run over the quota.
+ * It allows aliasing problems around the scheduler_tick to be
+ * less harmful.
*/
- if (!rt_task(p) && --rq_quota(rq, rq->prio_level) <= 0) {
+ if (!rt_task(p) && --rq_quota(rq, rq->prio_level) < 0) {
if (unlikely(p->first_time_slice))
p->first_time_slice = 0;
rotate_runqueue_priority(rq);
--
-ck
-
