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From: Gregory Haskins <ghaskins@novell.com>
To: linux-rt-users@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Gregory Haskins <ghaskins@novell.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Dmitry Adamushko <dmitry.adamushko@gmail.com>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@elte.hu>, Darren Hart <dvhltc@us.ibm.com>
Subject: [PATCH 06/13] RT: Maintain the highest RQ priority
Date: Tue, 23 Oct 2007 12:50:54 -0400	[thread overview]
Message-ID: <20071023165054.5536.13480.stgit@novell1.haskins.net> (raw)
In-Reply-To: <20071023164156.5536.95573.stgit@novell1.haskins.net>

This is an implementation of Steve's idea where we should update the RQ
concept of priority to show the highest-task, even if that task is not (yet)
running.  This prevents us from pushing multiple tasks to the RQ before it
gets a chance to reschedule.

Signed-off-by: Gregory Haskins <ghaskins@novell.com>
---

 kernel/sched.c |   34 +++++++++++++++++++++++++---------
 1 files changed, 25 insertions(+), 9 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 7c4fba8..c17e2e4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -304,7 +304,7 @@ struct rq {
 #ifdef CONFIG_PREEMPT_RT
 	unsigned long rt_nr_running;
 	unsigned long rt_nr_uninterruptible;
-	int curr_prio;
+	int highest_prio;
 #endif
 
 	unsigned long switch_timestamp;
@@ -368,11 +368,20 @@ static DEFINE_MUTEX(sched_hotcpu_mutex);
 #if defined(CONFIG_PREEMPT_RT) && defined(CONFIG_SMP)
 static inline void set_rq_prio(struct rq *rq, int prio)
 {
-	rq->curr_prio = prio;
+	rq->highest_prio = prio;
+}
+
+static inline void update_rq_prio(struct rq *rq)
+{
+	struct rt_prio_array *array = &rq->rt.active;
+	int                   prio  = sched_find_first_bit(array->bitmap);
+
+	set_rq_prio(rq, prio);
 }
 
 #else
 #define set_rq_prio(rq, prio) do { } while(0)
+#define update_rq_prio(rq)    do { } while(0)
 #endif
 
 static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
@@ -1023,12 +1032,14 @@ static void enqueue_task(struct rq *rq, struct task_struct *p, int wakeup)
 	sched_info_queued(p);
 	p->sched_class->enqueue_task(rq, p, wakeup);
 	p->se.on_rq = 1;
+	update_rq_prio(rq);
 }
 
 static void dequeue_task(struct rq *rq, struct task_struct *p, int sleep)
 {
 	p->sched_class->dequeue_task(rq, p, sleep);
 	p->se.on_rq = 0;
+	update_rq_prio(rq);
 }
 
 /*
@@ -1526,15 +1537,15 @@ static struct rq *find_lock_lowest_rq(cpumask_t *cpu_mask,
 				continue;
 
 			/* We look for lowest RT prio or non-rt CPU */
-			if (rq->curr_prio >= MAX_RT_PRIO) {
+			if (rq->highest_prio >= MAX_RT_PRIO) {
 				lowest_rq = rq;
 				dst_cpu = cpu;
 				break;
 			}
 
 			/* no locking for now */
-			if (rq->curr_prio > task->prio &&
-			    (!lowest_rq || rq->curr_prio < lowest_rq->curr_prio)) {
+			if (rq->highest_prio > task->prio &&
+			    (!lowest_rq || rq->highest_prio < lowest_rq->highest_prio)) {
 				lowest_rq = rq;
 				dst_cpu = cpu;
 			}
@@ -1560,7 +1571,7 @@ static struct rq *find_lock_lowest_rq(cpumask_t *cpu_mask,
 		}
 
 		/* If this rq is still suitable use it. */
-		if (lowest_rq->curr_prio > task->prio)
+		if (lowest_rq->highest_prio > task->prio)
 			break;
 
 		/* try again */
@@ -2339,10 +2350,8 @@ static inline void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	 */
 	prev_state = prev->state;
 	_finish_arch_switch(prev);
-
-	set_rq_prio(rq, current->prio);
-
 	finish_lock_switch(rq, prev);
+
 #if defined(CONFIG_PREEMPT_RT) && defined(CONFIG_SMP)
 	/*
 	 * If we pushed an RT task off the runqueue,
@@ -4647,6 +4656,9 @@ void rt_mutex_setprio(struct task_struct *p, int prio)
 	prev_resched = _need_resched();
 
 	if (on_rq) {
+		/*
+		 * Note: RQ priority gets updated in the enqueue/dequeue logic
+		 */
 		enqueue_task(rq, p, 0);
 		/*
 		 * Reschedule if we are currently running on this runqueue and
@@ -4713,6 +4725,10 @@ void set_user_nice(struct task_struct *p, long nice)
 		 */
 		if (delta < 0 || (delta > 0 && task_running(rq, p)))
 			resched_task(rq->curr);
+
+		/*
+		 * Note: RQ priority gets updated in the enqueue/dequeue logic
+		 */
 	}
 out_unlock:
 	task_rq_unlock(rq, &flags);


  parent reply	other threads:[~2007-10-23 17:07 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-10-23 16:50 [PATCH 00/13] Balance RT tasks v5 Gregory Haskins
2007-10-23 16:50 ` [PATCH 01/13] RT: push-rt Gregory Haskins
2007-10-23 16:50 ` [PATCH 02/13] RT: Condense the next-task search into one function Gregory Haskins
2007-10-23 16:50 ` [PATCH 03/13] RT: Add a per-cpu rt_overload indication Gregory Haskins
2007-10-23 16:50 ` [PATCH 04/13] RT: Wrap the RQ notion of priority to make it conditional Gregory Haskins
2007-10-23 16:50 ` [PATCH 05/13] RT: Initialize the priority value Gregory Haskins
2007-10-23 16:50 ` Gregory Haskins [this message]
2007-10-23 16:50 ` [PATCH 07/13] RT: Clean up some of the push-rt logic Gregory Haskins
2007-10-23 16:51 ` [PATCH 08/13] RT: Add support for low-priority wake-up to push_rt feature Gregory Haskins
2007-10-23 16:51 ` [PATCH 09/13] RT: Only dirty a cacheline if the priority is actually changing Gregory Haskins
2007-10-23 16:51 ` [PATCH 10/13] RT: Fixes for push-rt patch Gregory Haskins
2007-10-23 16:51 ` [PATCH 11/13] RT: Condense NORMAL and IDLE priorities Gregory Haskins
2007-10-23 16:51 ` [PATCH 12/13] RT: CPU priority management Gregory Haskins
2007-10-23 16:51 ` [PATCH 13/13] RT: Cache cpus_allowed weight for optimizing migration Gregory Haskins
2007-10-24  0:19   ` Ingo Oeser
2007-10-24  3:20     ` Gregory Haskins

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