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Date: Fri, 07 Jun 2013 15:37:43 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>, Kirill Tkhai <tkhai@...dex.ru>
Subject: [PATCH] sched/rt: Simplify pull_rt_task() logic and remove
.leaf_rt_rq_list
[ Peter, this is based off of some of my work, I ran it though a few
tests and it passed. I also reviewed it, and added my SOB as I am
somewhat a co-author to it. ]
From: Kirill Tkhai <tkhai@...dex.ru>
Based on the patch by Steven Rostedt from previous year:
https://lkml.org/lkml/2012/4/18/517
1)Simplify pull_rt_task() logic: search in pushable tasks of dest runqueue.
The only pullable tasks are the tasks which are pushable in their local rq,
and no others.
2)Remove .leaf_rt_rq_list member of struct rt_rq and functions connected
with it: nobody uses it since now.
Link: http://lkml.kernel.org/r/287571370557898@web7d.yandex.ru
Signed-off-by: Kirill Tkhai <tkhai@...dex.ru>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
kernel/sched/rt.c | 82 ++++++++++----------------------------------------
kernel/sched/sched.h | 1 -
2 files changed, 16 insertions(+), 67 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 8d85f9a..01970c8 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -399,20 +399,6 @@ static inline struct task_group *next_task_group(struct task_group *tg)
(iter = next_task_group(iter)) && \
(rt_rq = iter->rt_rq[cpu_of(rq)]);)
-static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
-{
- list_add_rcu(&rt_rq->leaf_rt_rq_list,
- &rq_of_rt_rq(rt_rq)->leaf_rt_rq_list);
-}
-
-static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
-{
- list_del_rcu(&rt_rq->leaf_rt_rq_list);
-}
-
-#define for_each_leaf_rt_rq(rt_rq, rq) \
- list_for_each_entry_rcu(rt_rq, &rq->leaf_rt_rq_list, leaf_rt_rq_list)
-
#define for_each_sched_rt_entity(rt_se) \
for (; rt_se; rt_se = rt_se->parent)
@@ -509,17 +495,6 @@ typedef struct rt_rq *rt_rq_iter_t;
#define for_each_rt_rq(rt_rq, iter, rq) \
for ((void) iter, rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
-static inline void list_add_leaf_rt_rq(struct rt_rq *rt_rq)
-{
-}
-
-static inline void list_del_leaf_rt_rq(struct rt_rq *rt_rq)
-{
-}
-
-#define for_each_leaf_rt_rq(rt_rq, rq) \
- for (rt_rq = &rq->rt; rt_rq; rt_rq = NULL)
-
#define for_each_sched_rt_entity(rt_se) \
for (; rt_se; rt_se = NULL)
@@ -1066,9 +1041,6 @@ static void __enqueue_rt_entity(struct sched_rt_entity *rt_se, bool head)
if (group_rq && (rt_rq_throttled(group_rq) || !group_rq->rt_nr_running))
return;
- if (!rt_rq->rt_nr_running)
- list_add_leaf_rt_rq(rt_rq);
-
if (head)
list_add(&rt_se->run_list, queue);
else
@@ -1088,8 +1060,6 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se)
__clear_bit(rt_se_prio(rt_se), array->bitmap);
dec_rt_tasks(rt_se, rt_rq);
- if (!rt_rq->rt_nr_running)
- list_del_leaf_rt_rq(rt_rq);
}
/*
@@ -1394,42 +1364,24 @@ static int pick_rt_task(struct rq *rq, struct task_struct *p, int cpu)
return 0;
}
-/* Return the second highest RT task, NULL otherwise */
-static struct task_struct *pick_next_highest_task_rt(struct rq *rq, int cpu)
+/*
+ * Return the highest pushable rq's task, which is suitable to be executed
+ * on the cpu, NULL otherwise
+ */
+static struct task_struct *pick_highest_pushable_task(struct rq *rq, int cpu)
{
- struct task_struct *next = NULL;
- struct sched_rt_entity *rt_se;
- struct rt_prio_array *array;
- struct rt_rq *rt_rq;
- int idx;
-
- for_each_leaf_rt_rq(rt_rq, rq) {
- array = &rt_rq->active;
- idx = sched_find_first_bit(array->bitmap);
-next_idx:
- if (idx >= MAX_RT_PRIO)
- continue;
- if (next && next->prio <= idx)
- continue;
- list_for_each_entry(rt_se, array->queue + idx, run_list) {
- struct task_struct *p;
+ struct plist_head *head = &rq->rt.pushable_tasks;
+ struct task_struct *p;
- if (!rt_entity_is_task(rt_se))
- continue;
+ if (!has_pushable_tasks(rq))
+ return NULL;
- p = rt_task_of(rt_se);
- if (pick_rt_task(rq, p, cpu)) {
- next = p;
- break;
- }
- }
- if (!next) {
- idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
- goto next_idx;
- }
+ plist_for_each_entry(p, head, pushable_tasks) {
+ if (pick_rt_task(rq, p, cpu))
+ return p;
}
- return next;
+ return NULL;
}
static DEFINE_PER_CPU(cpumask_var_t, local_cpu_mask);
@@ -1703,12 +1655,10 @@ static int pull_rt_task(struct rq *this_rq)
double_lock_balance(this_rq, src_rq);
/*
- * Are there still pullable RT tasks?
+ * We can pull only a task, which is pushable
+ * on its rq, and no others.
*/
- if (src_rq->rt.rt_nr_running <= 1)
- goto skip;
-
- p = pick_next_highest_task_rt(src_rq, this_cpu);
+ p = pick_highest_pushable_task(src_rq, this_cpu);
/*
* Do we have an RT task that preempts
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 74ff659..029601a 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -361,7 +361,6 @@ struct rt_rq {
unsigned long rt_nr_boosted;
struct rq *rq;
- struct list_head leaf_rt_rq_list;
struct task_group *tg;
#endif
};
--
1.7.3.4
--
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