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Message-Id: <200704190948.36649.kernel@kolivas.org>
Date: Thu, 19 Apr 2007 09:48:36 +1000
From: Con Kolivas <kernel@...ivas.org>
To: linux kernel mailing list <linux-kernel@...r.kernel.org>,
ck list <ck@....kolivas.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] sched: implement staircase deadline scheduler further improvements
While the Staircase Deadline scheduler has not been completely killed off and
is still in -mm I would like to fix some outstanding issues that I've found
since it still serves for comparison with all the upcoming schedulers.
While still in -mm can we queue this on top please?
A set of staircase-deadline v 0.41 patches will make their way into the usual
place for those willing to test it.
http://ck.kolivas.org/patches/staircase-deadline/
---
The prio_level was being inappropriately decreased if a higher priority
task was still using previous timeslice. Fix that.
Task expiration of higher priority tasks was not being taken into account
with allocating priority slots. Check the expired best_static_prio level
to facilitate that.
Explicitly check all better static priority prio_levels when deciding on
allocating slots for niced tasks.
These changes improve behaviour in many ways.
Signed-off-by: Con Kolivas <kernel@...ivas.org>
---
kernel/sched.c | 61 ++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 41 insertions(+), 20 deletions(-)
Index: linux-2.6.21-rc7-sd/kernel/sched.c
===================================================================
--- linux-2.6.21-rc7-sd.orig/kernel/sched.c 2007-04-19 08:51:54.000000000 +1000
+++ linux-2.6.21-rc7-sd/kernel/sched.c 2007-04-19 09:30:39.000000000 +1000
@@ -145,6 +145,12 @@ struct prio_array {
*/
DECLARE_BITMAP(prio_bitmap, MAX_PRIO + 1);
+ /*
+ * The best static priority (of the dynamic priority tasks) queued
+ * this array.
+ */
+ int best_static_prio;
+
#ifdef CONFIG_SMP
/* For convenience looks back at rq */
struct rq *rq;
@@ -191,9 +197,9 @@ struct rq {
/*
* The current dynamic priority level this runqueue is at per static
- * priority level, and the best static priority queued this rotation.
+ * priority level.
*/
- int prio_level[PRIO_RANGE], best_static_prio;
+ int prio_level[PRIO_RANGE];
/* How many times we have rotated the priority queue */
unsigned long prio_rotation;
@@ -669,7 +675,7 @@ static void task_new_array(struct task_s
}
/* Find the first slot from the relevant prio_matrix entry */
-static inline int first_prio_slot(struct task_struct *p)
+static int first_prio_slot(struct task_struct *p)
{
if (unlikely(p->policy == SCHED_BATCH))
return p->static_prio;
@@ -682,11 +688,18 @@ static inline int first_prio_slot(struct
* level. SCHED_BATCH tasks do not use the priority matrix. They only take
* priority slots from their static_prio and above.
*/
-static inline int next_entitled_slot(struct task_struct *p, struct rq *rq)
+static int next_entitled_slot(struct task_struct *p, struct rq *rq)
{
+ int search_prio = MAX_RT_PRIO, uprio = USER_PRIO(p->static_prio);
+ struct prio_array *array = rq->active;
DECLARE_BITMAP(tmp, PRIO_RANGE);
- int search_prio, uprio = USER_PRIO(p->static_prio);
+ /*
+ * Go straight to expiration if there are higher priority tasks
+ * already expired.
+ */
+ if (p->static_prio > rq->expired->best_static_prio)
+ return MAX_PRIO;
if (!rq->prio_level[uprio])
rq->prio_level[uprio] = MAX_RT_PRIO;
/*
@@ -694,15 +707,21 @@ static inline int next_entitled_slot(str
* static_prio are acceptable, and only if it's not better than
* a queued better static_prio's prio_level.
*/
- if (p->static_prio < rq->best_static_prio) {
- search_prio = MAX_RT_PRIO;
+ if (p->static_prio < array->best_static_prio) {
if (likely(p->policy != SCHED_BATCH))
- rq->best_static_prio = p->static_prio;
- } else if (p->static_prio == rq->best_static_prio)
+ array->best_static_prio = p->static_prio;
+ } else if (p->static_prio == array->best_static_prio) {
search_prio = rq->prio_level[uprio];
- else {
+ } else {
+ int i;
+
+ /* A bound O(n) function, worst case n is 40 */
+ for (i = array->best_static_prio; i <= p->static_prio ; i++) {
+ if (!rq->prio_level[USER_PRIO(i)])
+ rq->prio_level[USER_PRIO(i)] = MAX_RT_PRIO;
search_prio = max(rq->prio_level[uprio],
- rq->prio_level[USER_PRIO(rq->best_static_prio)]);
+ rq->prio_level[USER_PRIO(i)]);
+ }
}
if (unlikely(p->policy == SCHED_BATCH)) {
search_prio = max(search_prio, p->static_prio);
@@ -718,6 +737,8 @@ static void queue_expired(struct task_st
{
task_new_array(p, rq, rq->expired);
p->prio = p->normal_prio = first_prio_slot(p);
+ if (p->static_prio < rq->expired->best_static_prio)
+ rq->expired->best_static_prio = p->static_prio;
}
#ifdef CONFIG_SMP
@@ -726,7 +747,7 @@ static void queue_expired(struct task_st
* update its data appropriately. Note we may be reading data from src_rq->
* outside of lock, but the occasional inaccurate result should be harmless.
*/
- static inline void update_if_moved(struct task_struct *p, struct rq *rq)
+ static void update_if_moved(struct task_struct *p, struct rq *rq)
{
struct rq *src_rq = p->array->rq;
@@ -3217,8 +3238,10 @@ EXPORT_SYMBOL(sub_preempt_count);
#endif
-static inline void reset_prio_levels(struct rq *rq)
+static void reset_prio_levels(struct rq *rq)
{
+ rq->active->best_static_prio = MAX_PRIO - 1;
+ rq->expired->best_static_prio = MAX_PRIO - 1;
memset(rq->prio_level, 0, sizeof(int) * PRIO_RANGE);
}
@@ -3239,7 +3262,6 @@ retry:
rq->active = array;
rq->exp_bitmap = rq->expired->prio_bitmap;
rq->dyn_bitmap = rq->active->prio_bitmap;
- rq->best_static_prio = MAX_PRIO - 1;
rq->prio_rotation++;
idx = find_next_bit(rq->dyn_bitmap, MAX_PRIO, MAX_RT_PRIO);
reset_prio_levels(rq);
@@ -3261,9 +3283,10 @@ retry:
if (likely(next->policy != SCHED_BATCH)) {
int nstatic = next->static_prio;
- if (nstatic < rq->best_static_prio)
- rq->best_static_prio = nstatic;
- rq->prio_level[USER_PRIO(nstatic)] = idx;
+ if (nstatic < array->best_static_prio)
+ array->best_static_prio = nstatic;
+ if (idx > rq->prio_level[USER_PRIO(nstatic)])
+ rq->prio_level[USER_PRIO(nstatic)] = idx;
}
return next;
}
@@ -3348,7 +3371,6 @@ need_resched_nonpreemptible:
}
switch_tasks:
if (next == rq->idle) {
- rq->best_static_prio = MAX_PRIO - 1;
reset_prio_levels(rq);
rq->prio_rotation++;
schedstat_inc(rq, sched_goidle);
@@ -6671,10 +6693,9 @@ void __init sched_init(void)
lockdep_set_class(&rq->lock, &rq->rq_lock_key);
rq->nr_running = 0;
rq->prio_rotation = 0;
- rq->best_static_prio = MAX_PRIO - 1;
- reset_prio_levels(rq);
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
+ reset_prio_levels(rq);
rq->dyn_bitmap = rq->active->prio_bitmap;
rq->exp_bitmap = rq->expired->prio_bitmap;
--
-ck
-
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