Commit c9819f45 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
Browse files

[PATCH] sched: use softirq for load balancing 



Call rebalance_tick (renamed to run_rebalance_domains) from a newly introduced
softirq.

We calculate the earliest time for each layer of sched domains to be rescanned
(this is the rescan time for idle) and use the earliest of those to schedule
the softirq via a new field "next_balance" added to struct rq.

Signed-off-by: default avatarChristoph Lameter <clameter@sgi.com>
Cc: Peter Williams <pwil3058@bigpond.net.au>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
Cc: "Chen, Kenneth W" <kenneth.w.chen@intel.com>
Acked-by: default avatarIngo Molnar <mingo@elte.hu>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent e418e1c2

include/linux/interrupt.h

+2 −1
Original line number Diff line number Diff line
@@ -231,7 +231,8 @@ enum 
	NET_TX_SOFTIRQ,

	NET_RX_SOFTIRQ,

	BLOCK_SOFTIRQ,

	TASKLET_SOFTIRQ

	TASKLET_SOFTIRQ,

	SCHED_SOFTIRQ,

};



/* softirq mask and active fields moved to irq_cpustat_t in

kernel/sched.c

+17 −5
Original line number Diff line number Diff line
@@ -227,6 +227,7 @@ struct rq { 
	unsigned long expired_timestamp;

	unsigned long long timestamp_last_tick;

	struct task_struct *curr, *idle;

	unsigned long next_balance;

	struct mm_struct *prev_mm;

	struct prio_array *active, *expired, arrays[2];

	int best_expired_prio;
@@ -2858,7 +2859,7 @@ static void update_load(struct rq *this_rq) 
}



/*

 * rebalance_tick will get called every timer tick, on every CPU.

 * run_rebalance_domains is triggered when needed from the scheduler tick.

 *

 * It checks each scheduling domain to see if it is due to be balanced,

 * and initiates a balancing operation if so.
@@ -2866,9 +2867,10 @@ static void update_load(struct rq *this_rq) 
 * Balancing parameters are set up in arch_init_sched_domains.

 */



static void

rebalance_tick(int this_cpu, struct rq *this_rq)

static void run_rebalance_domains(struct softirq_action *h)

{

	int this_cpu = smp_processor_id();

	struct rq *this_rq = cpu_rq(this_cpu);

	unsigned long interval;

	struct sched_domain *sd;

	/*
@@ -2877,6 +2879,8 @@ rebalance_tick(int this_cpu, struct rq *this_rq) 
	 */

	enum idle_type idle = !this_rq->nr_running ?

				SCHED_IDLE : NOT_IDLE;

	/* Earliest time when we have to call run_rebalance_domains again */

	unsigned long next_balance = jiffies + 60*HZ;



	for_each_domain(this_cpu, sd) {

		if (!(sd->flags & SD_LOAD_BALANCE))
@@ -2891,7 +2895,7 @@ rebalance_tick(int this_cpu, struct rq *this_rq) 
		if (unlikely(!interval))

			interval = 1;



		if (jiffies - sd->last_balance >= interval) {

		if (time_after_eq(jiffies, sd->last_balance + interval)) {

			if (load_balance(this_cpu, this_rq, sd, idle)) {

				/*

				 * We've pulled tasks over so either we're no
@@ -2902,7 +2906,10 @@ rebalance_tick(int this_cpu, struct rq *this_rq) 
			}

			sd->last_balance += interval;

		}

		if (time_after(next_balance, sd->last_balance + interval))

			next_balance = sd->last_balance + interval;

	}

	this_rq->next_balance = next_balance;

}

#else

/*
@@ -3155,7 +3162,8 @@ void scheduler_tick(void) 
		task_running_tick(rq, p);

#ifdef CONFIG_SMP

	update_load(rq);

	rebalance_tick(cpu, rq);

	if (time_after_eq(jiffies, rq->next_balance))

		raise_softirq(SCHED_SOFTIRQ);

#endif

}
@@ -6859,6 +6867,10 @@ void __init sched_init(void) 


	set_load_weight(&init_task);



#ifdef CONFIG_SMP

	open_softirq(SCHED_SOFTIRQ, run_rebalance_domains, NULL);

#endif



#ifdef CONFIG_RT_MUTEXES

	plist_head_init(&init_task.pi_waiters, &init_task.pi_lock);

#endif

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