[PATCH 4/5] Create rebalance_domains from rebalance_tick

Christoph Lameter
2006-10-24T18:31:47Z

Create rebalance_domains() from rebalance_tick().

Essentially rebalance_domains = rebalance_tick. However, we
do the idle calculation on our own. This removes some processing
from scheduler_tick into rebalance_domains().

While we are at it: Take the opportunity to avoid taking
the request queue lock in wake_priority_sleeper if
there are no running processes.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.19-rc2-mm2/kernel/sched.c
===================================================================
--- linux-2.6.19-rc2-mm2.orig/kernel/sched.c 2006-10-24 10:39:13.782726627 -0500
+++ linux-2.6.19-rc2-mm2/kernel/sched.c 2006-10-24 10:40:32.928543506 -0500
@@ -2842,18 +2842,22 @@ static void update_load(struct rq *this_
}

/*
- * rebalance_tick will get called every timer tick, on every CPU.
+ * rebalance_domains is called 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.
*
* Balancing parameters are set up in arch_init_sched_domains.
*/
-static void
-rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
+static void rebalance_domains(unsigned long dummy)
{
+ int this_cpu = smp_processor_id();
+ struct rq *this_rq = cpu_rq(this_cpu);
unsigned long interval;
struct sched_domain *sd;
+ /* Idle means on the idle queue without a runnable task */
+ enum idle_type idle = (this_rq->idle && !this_rq->nr_running) ?
+ SCHED_IDLE : NOT_IDLE;

for_each_domain(this_cpu, sd) {
if (!(sd->flags & SD_LOAD_BALANCE))
@@ -2885,34 +2889,26 @@ rebalance_tick(int this_cpu, struct rq *
/*
* on UP we do not need to balance between CPUs:
*/
-static inline void rebalance_tick(int cpu, struct rq *rq, enum idle_type idle)
-{
-}
static inline void idle_balance(int cpu, struct rq *rq)
{
}
-static inline void update_load(struct rq *this_rq)
-{
-}
#endif

-static inline int wake_priority_sleeper(struct rq *rq)
+static inline void wake_priority_sleeper(struct rq *rq)
{
- int ret = 0;
-
#ifdef CONFIG_SCHED_SMT
+ if (!rq->nr_running)
+ return;
+
spin_lock(&rq->lock);
/*
* If an SMT sibling task has been put to sleep for priority
* reasons reschedule the idle task to see if it can now run.
*/
- if (rq->nr_running) {
+ if (rq->nr_running)
resched_task(rq->idle);
- ret = 1;
- }
spin_unlock(&rq->lock);
#endif
- return ret;
}

DEFINE_PER_CPU(struct kernel_stat, kstat);
@@ -3123,17 +3119,15 @@ void scheduler_tick(void)
struct task_struct *p = current;
int cpu = smp_processor_id();
struct rq *rq = cpu_rq(cpu);
- enum idle_type idle = NOT_IDLE;

update_cpu_clock(p, rq, now);

rq->timestamp_last_tick = now;

- if (p == rq->idle) {
+ if (p == rq->idle)
/* Task on the idle queue */
- if (!wake_priority_sleeper(rq))
- idle = SCHED_IDLE;
- } else {
+ wake_priority_sleeper(rq);
+ else {
/* Task on cpu queue */
if (p->array != rq->active)
/* Task has expired but was not scheduled yet */
@@ -3141,8 +3135,10 @@ void scheduler_tick(void)
else
time_slice(rq, p);
}
+#ifdef CONFIG_SMP
update_load(rq);
- rebalance_tick(cpu, rq, idle);
+ rebalance_domains(0L);
+#endif
}

#ifdef CONFIG_SCHED_SMT