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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 2/3] Subject: SCHED - Only balance our RT tasks within our root-domain
Date: Tue, 04 Dec 2007 21:55:33 -0500	[thread overview]
Message-ID: <20071205025533.4494.63786.stgit@novell1.haskins.net> (raw)
In-Reply-To: <20071205025137.4494.18683.stgit@novell1.haskins.net>

We move the rt-overload data as the first global to per-domain
reclassification.  This limits the scope of overload related cache-line
bouncing to stay with a specified partition instead of affecting all
cpus in the system.

Finally, we limit the scope of find_lowest_cpu searches to the domain
instead of the entire system.  Note that we would always respect domain
boundaries even without this patch, but we first would scan potentially
all cpus before whittling the list down.  Now we can avoid looking at
RQs that are out of scope, again reducing cache-line hits.

Note: In some cases, task->cpus_allowed will effectively reduce our search
to within our domain.  However, I believe there are cases where the
cpus_allowed mask may be all ones and therefore we err on the side of
caution.  If it can be optimized later, so be it.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
CC: Christoph Lameter <clameter@sgi.com>
---

 kernel/sched.c    |    7 +++++++
 kernel/sched_rt.c |   57 +++++++++++++++++++++++++++++------------------------
 2 files changed, 38 insertions(+), 26 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index dfb939f..9a09f82 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -367,6 +367,13 @@ struct root_domain {
 	atomic_t refcount;
 	cpumask_t span;
 	cpumask_t online;
+
+        /*
+	 * The "RT overload" flag: it gets set if a CPU has more than
+	 * one runnable RT task.
+	 */
+	cpumask_t rto_mask;
+	atomic_t  rto_count;
 };
 
 static struct root_domain def_root_domain;
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 9dcf522..f9728d0 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -5,22 +5,14 @@
 
 #ifdef CONFIG_SMP
 
-/*
- * The "RT overload" flag: it gets set if a CPU has more than
- * one runnable RT task.
- */
-static cpumask_t rt_overload_mask;
-static atomic_t rto_count;
-
-static inline int rt_overloaded(void)
+static inline int rt_overloaded(struct rq *rq)
 {
-	return atomic_read(&rto_count);
+	return atomic_read(&rq->rd->rto_count);
 }
 
 static inline void rt_set_overload(struct rq *rq)
 {
-	rq->rt.overloaded = 1;
-	cpu_set(rq->cpu, rt_overload_mask);
+	cpu_set(rq->cpu, rq->rd->rto_mask);
 	/*
 	 * Make sure the mask is visible before we set
 	 * the overload count. That is checked to determine
@@ -29,23 +21,25 @@ static inline void rt_set_overload(struct rq *rq)
 	 * updated yet.
 	 */
 	wmb();
-	atomic_inc(&rto_count);
+	atomic_inc(&rq->rd->rto_count);
 }
 
 static inline void rt_clear_overload(struct rq *rq)
 {
 	/* the order here really doesn't matter */
-	atomic_dec(&rto_count);
-	cpu_clear(rq->cpu, rt_overload_mask);
-	rq->rt.overloaded = 0;
+	atomic_dec(&rq->rd->rto_count);
+	cpu_clear(rq->cpu, rq->rd->rto_mask);
 }
 
 static void update_rt_migration(struct rq *rq)
 {
-	if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1))
+	if (rq->rt.rt_nr_migratory && (rq->rt.rt_nr_running > 1)) {
 		rt_set_overload(rq);
-	else
+		rq->rt.overloaded = 1;
+	} else {
 		rt_clear_overload(rq);
+		rq->rt.overloaded = 0;
+	}
 }
 #endif /* CONFIG_SMP */
 
@@ -306,7 +300,7 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 	int       count       = 0;
 	int       cpu;
 
-	cpus_and(*lowest_mask, cpu_online_map, task->cpus_allowed);
+	cpus_and(*lowest_mask, task_rq(task)->rd->online, task->cpus_allowed);
 
 	/*
 	 * Scan each rq for the lowest prio.
@@ -580,18 +574,12 @@ static int pull_rt_task(struct rq *this_rq)
 	struct task_struct *p, *next;
 	struct rq *src_rq;
 
-	/*
-	 * If cpusets are used, and we have overlapping
-	 * run queue cpusets, then this algorithm may not catch all.
-	 * This is just the price you pay on trying to keep
-	 * dirtying caches down on large SMP machines.
-	 */
-	if (likely(!rt_overloaded()))
+	if (likely(!rt_overloaded(this_rq)))
 		return 0;
 
 	next = pick_next_task_rt(this_rq);
 
-	for_each_cpu_mask(cpu, rt_overload_mask) {
+	for_each_cpu_mask(cpu, this_rq->rd->rto_mask) {
 		if (this_cpu == cpu)
 			continue;
 
@@ -809,6 +797,20 @@ static void task_tick_rt(struct rq *rq, struct task_struct *p)
 	}
 }
 
+/* Assumes rq->lock is held */
+static void join_domain_rt(struct rq *rq)
+{
+	if (rq->rt.overloaded)
+		rt_set_overload(rq);
+}
+
+/* Assumes rq->lock is held */
+static void leave_domain_rt(struct rq *rq)
+{
+	if (rq->rt.overloaded)
+		rt_clear_overload(rq);
+}
+
 static void set_curr_task_rt(struct rq *rq)
 {
 	struct task_struct *p = rq->curr;
@@ -838,4 +840,7 @@ const struct sched_class rt_sched_class = {
 
 	.set_curr_task          = set_curr_task_rt,
 	.task_tick		= task_tick_rt,
+
+	.join_domain            = join_domain_rt,
+	.leave_domain           = leave_domain_rt,
 };


  parent reply	other threads:[~2007-12-05  3:18 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 ` [PATCH 07/23] Subject: SCHED - disable CFS RT load balancing Gregory Haskins
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     ` Gregory Haskins [this message]
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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