Messages in this thread Patch in this message | | | From | Con Kolivas <> | Subject | [PATCH] sched: implement staircase deadline scheduler further improvements | Date | Thu, 19 Apr 2007 09:48:36 +1000 |
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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@kolivas.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 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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