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From: Gregory Haskins <ghaskins@novell.com>
To: mingo@elte.hu
Cc: rostedt@goodmis.org, ghaskins@novell.com,
	linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 07/23] Subject: SCHED - disable CFS RT load balancing.
Date: Tue, 04 Dec 2007 15:45:01 -0500	[thread overview]
Message-ID: <20071204204501.3567.25517.stgit@novell1.haskins.net> (raw)
In-Reply-To: <20071204204236.3567.65491.stgit@novell1.haskins.net>

From: Steven Rostedt <srostedt@redhat.com>

Since we now take an active approach to load balancing, we don't need to
balance RT tasks via CFS. In fact, this code was found to pull RT tasks
away from CPUS that the active movement performed, resulting in
large latencies.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---

 kernel/sched_rt.c |   95 ++---------------------------------------------------
 1 files changed, 4 insertions(+), 91 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index a0b05ff..ea07ffa 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -565,109 +565,22 @@ static void wakeup_balance_rt(struct rq *rq, struct task_struct *p)
 		push_rt_tasks(rq);
 }
 
-/*
- * Load-balancing iterator. Note: while the runqueue stays locked
- * during the whole iteration, the current task might be
- * dequeued so the iterator has to be dequeue-safe. Here we
- * achieve that by always pre-iterating before returning
- * the current task:
- */
-static struct task_struct *load_balance_start_rt(void *arg)
-{
-	struct rq *rq = arg;
-	struct rt_prio_array *array = &rq->rt.active;
-	struct list_head *head, *curr;
-	struct task_struct *p;
-	int idx;
-
-	idx = sched_find_first_bit(array->bitmap);
-	if (idx >= MAX_RT_PRIO)
-		return NULL;
-
-	head = array->queue + idx;
-	curr = head->prev;
-
-	p = list_entry(curr, struct task_struct, run_list);
-
-	curr = curr->prev;
-
-	rq->rt.rt_load_balance_idx = idx;
-	rq->rt.rt_load_balance_head = head;
-	rq->rt.rt_load_balance_curr = curr;
-
-	return p;
-}
-
-static struct task_struct *load_balance_next_rt(void *arg)
-{
-	struct rq *rq = arg;
-	struct rt_prio_array *array = &rq->rt.active;
-	struct list_head *head, *curr;
-	struct task_struct *p;
-	int idx;
-
-	idx = rq->rt.rt_load_balance_idx;
-	head = rq->rt.rt_load_balance_head;
-	curr = rq->rt.rt_load_balance_curr;
-
-	/*
-	 * If we arrived back to the head again then
-	 * iterate to the next queue (if any):
-	 */
-	if (unlikely(head == curr)) {
-		int next_idx = find_next_bit(array->bitmap, MAX_RT_PRIO, idx+1);
-
-		if (next_idx >= MAX_RT_PRIO)
-			return NULL;
-
-		idx = next_idx;
-		head = array->queue + idx;
-		curr = head->prev;
-
-		rq->rt.rt_load_balance_idx = idx;
-		rq->rt.rt_load_balance_head = head;
-	}
-
-	p = list_entry(curr, struct task_struct, run_list);
-
-	curr = curr->prev;
-
-	rq->rt.rt_load_balance_curr = curr;
-
-	return p;
-}
-
 static unsigned long
 load_balance_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
 		unsigned long max_load_move,
 		struct sched_domain *sd, enum cpu_idle_type idle,
 		int *all_pinned, int *this_best_prio)
 {
-	struct rq_iterator rt_rq_iterator;
-
-	rt_rq_iterator.start = load_balance_start_rt;
-	rt_rq_iterator.next = load_balance_next_rt;
-	/* pass 'busiest' rq argument into
-	 * load_balance_[start|next]_rt iterators
-	 */
-	rt_rq_iterator.arg = busiest;
-
-	return balance_tasks(this_rq, this_cpu, busiest, max_load_move, sd,
-			     idle, all_pinned, this_best_prio, &rt_rq_iterator);
+	/* don't touch RT tasks */
+	return 0;
 }
 
 static int
 move_one_task_rt(struct rq *this_rq, int this_cpu, struct rq *busiest,
 		 struct sched_domain *sd, enum cpu_idle_type idle)
 {
-	struct rq_iterator rt_rq_iterator;
-
-	rt_rq_iterator.start = load_balance_start_rt;
-	rt_rq_iterator.next = load_balance_next_rt;
-	rt_rq_iterator.arg = busiest;
-
-	return iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
-				  &rt_rq_iterator);
+	/* don't touch RT tasks */
+	return 0;
 }
 #else /* CONFIG_SMP */
 # define schedule_tail_balance_rt(rq)	do { } while (0)


  parent reply	other threads:[~2007-12-04 21:09 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-04 20:44 [PATCH 00/23] RT balance v7 Gregory Haskins
2007-12-04 20:44 ` [PATCH 01/23] Subject: SCHED - Add rt_nr_running accounting Gregory Haskins
2007-12-04 20:44 ` [PATCH 02/23] Subject: SCHED - track highest prio queued on runqueue Gregory Haskins
2007-12-04 20:44 ` [PATCH 03/23] Subject: SCHED - push RT tasks Gregory Haskins
2007-12-04 20:44 ` [PATCH 04/23] Subject: SCHED - RT overloaded runqueues accounting Gregory Haskins
2007-12-04 20:44 ` [PATCH 05/23] Subject: SCHED - pull RT tasks Gregory Haskins
2007-12-04 20:44 ` [PATCH 06/23] Subject: SCHED - wake up balance RT Gregory Haskins
2007-12-04 20:45 ` Gregory Haskins [this message]
2007-12-04 20:45 ` [PATCH 08/23] Subject: SCHED - Cache cpus_allowed weight for optimizing migration Gregory Haskins
2007-12-04 20:45 ` [PATCH 09/23] Subject: SCHED - Consistency cleanup for this_rq usage Gregory Haskins
2007-12-04 20:45 ` [PATCH 10/23] Subject: SCHED - Remove some CFS specific code from the wakeup path of RT tasks Gregory Haskins
2007-12-04 20:45 ` [PATCH 11/23] Subject: SCHED - Break out the search function Gregory Haskins
2007-12-04 20:45 ` [PATCH 12/23] Subject: SCHED - Allow current_cpu to be included in search Gregory Haskins
2007-12-04 20:45 ` [PATCH 13/23] Subject: SCHED - Pre-route RT tasks on wakeup Gregory Haskins
2007-12-04 20:45 ` [PATCH 14/23] Subject: SCHED - Optimize our cpu selection based on topology Gregory Haskins
2007-12-04 20:45 ` [PATCH 15/23] Subject: SCHED - Optimize rebalancing Gregory Haskins
2007-12-04 20:45 ` [PATCH 16/23] Subject: SCHED - Avoid overload Gregory Haskins
2007-12-04 20:45 ` [PATCH 17/23] Subject: SCHED - restore the migratable conditional Gregory Haskins
2007-12-04 20:45 ` [PATCH 18/23] Subject: SCHED - Optimize cpu search with hamming weight Gregory Haskins
2007-12-04 20:46 ` [PATCH 19/23] Subject: SCHED - Optimize out cpu_clears Gregory Haskins
2007-12-04 20:46 ` [PATCH 20/23] Subject: SCHED - balance RT tasks no new wake up Gregory Haskins
2007-12-04 20:46 ` [PATCH 21/23] Subject: SCHED - Add sched-domain roots Gregory Haskins
2007-12-04 20:46 ` [PATCH 22/23] Subject: SCHED - Only balance our RT tasks within our root-domain Gregory Haskins
2007-12-04 20:46 ` [PATCH 23/23] Subject: SCHED - Use a 2-d bitmap for searching lowest-pri CPU Gregory Haskins
2007-12-04 21:27 ` [PATCH 00/23] RT balance v7 Ingo Molnar
2007-12-04 21:35   ` Gregory Haskins
2007-12-05  2:55   ` [PATCH 0/3] RT balance v7a Gregory Haskins
2007-12-05  2:55     ` [PATCH 1/3] Subject: SCHED - Add sched-domain roots Gregory Haskins
2007-12-05  2:55     ` [PATCH 2/3] Subject: SCHED - Only balance our RT tasks within our root-domain Gregory Haskins
2007-12-05  2:55     ` [PATCH 3/3] Subject: SCHED - Use a 2-d bitmap for searching lowest-pri CPU Gregory Haskins
2007-12-05  9:34       ` Ingo Molnar
2007-12-05 10:19         ` Gregory Haskins
2007-12-05 11:44           ` Ingo Molnar
2007-12-05 13:41             ` Gregory Haskins

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