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From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
To: mingo@elte.hu
Cc: linux-kernel@vger.kernel.org, npiggin@suse.de, rostedt@goodmis.org
Subject: [patch 1/2] sched: fix idle load balancing in softirqd context
Date: Fri, 16 Feb 2007 18:03:35 -0800	[thread overview]
Message-ID: <20070216180335.A8744@unix-os.sc.intel.com> (raw)
In-Reply-To: <20070130135709.B32010@unix-os.sc.intel.com>; from suresh.b.siddha@intel.com on Tue, Jan 30, 2007 at 01:57:09PM -0800

Periodic load balancing in recent kernels happen in the softirq.
In certain -rt configurations, these softirqs are handled in softirqd
context. And hence the check for idle processor was always returning
busy (as nr_running > 1).

This patch captures the idle information at the tick and passes this info
to softirq context through an element 'idle_at_tick' in rq.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
---

diff -pNru linux-2.6.20.x86_64/kernel/sched.c linux/kernel/sched.c
--- linux-2.6.20.x86_64/kernel/sched.c	2007-02-10 03:41:27.000000000 -0800
+++ linux/kernel/sched.c	2007-02-16 16:22:44.000000000 -0800
@@ -240,6 +240,7 @@ struct rq {
 	unsigned long raw_weighted_load;
 #ifdef CONFIG_SMP
 	unsigned long cpu_load[3];
+	unsigned char idle_at_tick;
 #endif
 	unsigned long long nr_switches;
 
@@ -3350,12 +3351,7 @@ static void run_rebalance_domains(struct
 	struct rq *this_rq = cpu_rq(this_cpu);
 	unsigned long interval;
 	struct sched_domain *sd;
-	/*
-	 * We are idle if there are no processes running. This
-	 * is valid even if we are the idle process (SMT).
-	 */
-	enum idle_type idle = !this_rq->nr_running ?
-				SCHED_IDLE : NOT_IDLE;
+	enum idle_type idle = this_rq->idle_at_tick ? SCHED_IDLE : NOT_IDLE;
 	/* Earliest time when we have to call run_rebalance_domains again */
 	unsigned long next_balance = jiffies + 60*HZ;
 
@@ -3651,20 +3647,21 @@ void scheduler_tick(void)
 {
 	unsigned long long now = sched_clock();
 	struct task_struct *p = current;
-	int cpu = smp_processor_id();
+	int cpu = smp_processor_id(), idle_at_tick = idle_cpu(cpu);
 	struct rq *rq = cpu_rq(cpu);
 
 	BUG_ON(!irqs_disabled());
 
 	update_cpu_clock(p, rq, now);
 
-	if (p == rq->idle)
+	if (idle_at_tick)
 		/* Task on the idle queue */
 		wake_priority_sleeper(rq);
 	else
 		task_running_tick(rq, p);
 #ifdef CONFIG_SMP
 	update_load(rq);
+	rq->idle_at_tick = idle_at_tick;
 	if (time_after_eq(jiffies, rq->next_balance))
 		raise_softirq(SCHED_SOFTIRQ);
 #endif

  parent reply	other threads:[~2007-02-17  2:38 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2006-12-11 23:53 [RFC] Patch: dynticks: idle load balancing Siddha, Suresh B
2006-12-13 22:43 ` Ingo Molnar
2006-12-13 23:13   ` Ingo Molnar
2006-12-13 23:03     ` Siddha, Suresh B
2006-12-13 23:31       ` Ingo Molnar
2006-12-13 23:19         ` Siddha, Suresh B
2006-12-14  0:34           ` Ingo Molnar
2006-12-19 20:12           ` Ingo Molnar
2006-12-19 21:12             ` Siddha, Suresh B
2007-01-16 11:35               ` Ingo Molnar
2007-01-30 21:57                 ` Siddha, Suresh B
2007-02-07 22:19                   ` Siddha, Suresh B
2007-02-17  2:03                   ` Siddha, Suresh B [this message]
2007-02-17  2:08                     ` [patch 2/2] sched: dynticks idle load balancing - v2 Siddha, Suresh B
2007-02-21 20:23                       ` Andrew Morton
2007-02-22  3:14                         ` Nick Piggin
2007-02-24  2:01                         ` [patch] sched: dynticks idle load balancing - v3 Siddha, Suresh B
2007-02-22  3:26                       ` [patch 2/2] sched: dynticks idle load balancing - v2 Nick Piggin
2007-02-22 22:33                         ` Siddha, Suresh B
2007-02-23  3:43                           ` Nick Piggin
2007-02-17 14:42                     ` [patch 1/2] sched: fix idle load balancing in softirqd context Steven Rostedt
2007-02-21  6:25                       ` Siddha, Suresh B
2007-02-21 20:13                     ` Andrew Morton
2006-12-13 23:48     ` [RFC] Patch: dynticks: idle load balancing Ingo Molnar
2006-12-20  0:49 ` Steven Rostedt

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