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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 19/23] Subject: SCHED - Optimize out cpu_clears
Date: Tue, 04 Dec 2007 15:46:01 -0500	[thread overview]
Message-ID: <20071204204601.3567.77236.stgit@novell1.haskins.net> (raw)
In-Reply-To: <20071204204236.3567.65491.stgit@novell1.haskins.net>

From: Steven Rostedt <srostedt@redhat.com>

This patch removes several cpumask operations by keeping track
of the first of the CPUS that is of the lowest priority. When
the search for the lowest priority runqueue is completed, all
the bits up to the first CPU with the lowest priority runqueue
is cleared.

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

 kernel/sched_rt.c |   49 ++++++++++++++++++++++++++++++++++++-------------
 1 files changed, 36 insertions(+), 13 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 0514b27..039be04 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -294,29 +294,36 @@ static struct task_struct *pick_next_highest_task_rt(struct rq *rq,
 }
 
 static DEFINE_PER_CPU(cpumask_t, local_cpu_mask);
-static DEFINE_PER_CPU(cpumask_t, valid_cpu_mask);
 
 static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 {
-	int       cpu;
-	cpumask_t *valid_mask = &__get_cpu_var(valid_cpu_mask);
 	int       lowest_prio = -1;
+	int       lowest_cpu  = -1;
 	int       count       = 0;
+	int       cpu;
 
-	cpus_clear(*lowest_mask);
-	cpus_and(*valid_mask, cpu_online_map, task->cpus_allowed);
+	cpus_and(*lowest_mask, cpu_online_map, task->cpus_allowed);
 
 	/*
 	 * Scan each rq for the lowest prio.
 	 */
-	for_each_cpu_mask(cpu, *valid_mask) {
+	for_each_cpu_mask(cpu, *lowest_mask) {
 		struct rq *rq = cpu_rq(cpu);
 
 		/* We look for lowest RT prio or non-rt CPU */
 		if (rq->rt.highest_prio >= MAX_RT_PRIO) {
-			if (count)
+			/*
+			 * if we already found a low RT queue
+			 * and now we found this non-rt queue
+			 * clear the mask and set our bit.
+			 * Otherwise just return the queue as is
+			 * and the count==1 will cause the algorithm
+			 * to use the first bit found.
+			 */
+			if (lowest_cpu != -1) {
 				cpus_clear(*lowest_mask);
-			cpu_set(rq->cpu, *lowest_mask);
+				cpu_set(rq->cpu, *lowest_mask);
+			}
 			return 1;
 		}
 
@@ -326,13 +333,29 @@ static int find_lowest_cpus(struct task_struct *task, cpumask_t *lowest_mask)
 			if (rq->rt.highest_prio > lowest_prio) {
 				/* new low - clear old data */
 				lowest_prio = rq->rt.highest_prio;
-				if (count) {
-					cpus_clear(*lowest_mask);
-					count = 0;
-				}
+				lowest_cpu = cpu;
+				count = 0;
 			}
-			cpu_set(rq->cpu, *lowest_mask);
 			count++;
+		} else
+			cpu_clear(cpu, *lowest_mask);
+	}
+
+	/*
+	 * Clear out all the set bits that represent
+	 * runqueues that were of higher prio than
+	 * the lowest_prio.
+	 */
+	if (lowest_cpu > 0) {
+		/*
+		 * Perhaps we could add another cpumask op to
+		 * zero out bits. Like cpu_zero_bits(cpumask, nrbits);
+		 * Then that could be optimized to use memset and such.
+		 */
+		for_each_cpu_mask(cpu, *lowest_mask) {
+			if (cpu >= lowest_cpu)
+				break;
+			cpu_clear(cpu, *lowest_mask);
 		}
 	}
 


  parent reply	other threads:[~2007-12-04 21:14 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 ` Gregory Haskins [this message]
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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