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Subject[PATCH 2/5] Extract load calculation from rebalance_tick
Extract load calculation from rebalance_tick

A load calculation is always done in rebalance_tick() in addition
to the real load balancing activities that only take place when certain
jiffie counts have been reached. Move that processing into a separate
function and call it directly from scheduler_tick().

Also extract the time slice handling from scheduler_tick and
put it into a separate function. Then we can clean up scheduler_tick
significantly. It will no longer have any gotos.

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 2006-10-23 20:13:02.393266962 -0500
+++ linux-2.6.19-rc2-mm2/kernel/sched.c 2006-10-24 10:39:07.158552011 -0500
@@ -2817,27 +2817,10 @@ static void active_load_balance(struct r
spin_unlock(&target_rq->lock);
}

-/*
- * rebalance_tick will get called every timer tick, on every CPU.
- *
- * 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.
- */
-
-/* Don't have all balancing operations going off at once: */
-static inline unsigned long cpu_offset(int cpu)
+static void update_load(struct rq *this_rq)
{
- return jiffies + cpu * HZ / NR_CPUS;
-}
-
-static void
-rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
-{
- unsigned long this_load, interval, j = cpu_offset(this_cpu);
- struct sched_domain *sd;
int i, scale;
+ unsigned long this_load;

this_load = this_rq->raw_weighted_load;

@@ -2856,6 +2839,28 @@ rebalance_tick(int this_cpu, struct rq *
new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
}
+}
+
+/*
+ * rebalance_tick will get called every timer tick, on every CPU.
+ *
+ * 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.
+ */
+
+/* Don't have all balancing operations going off at once: */
+static inline unsigned long cpu_offset(int cpu)
+{
+ return jiffies + cpu * HZ / NR_CPUS;
+}
+
+static void
+rebalance_tick(int this_cpu, struct rq *this_rq, enum idle_type idle)
+{
+ unsigned long interval, j = cpu_offset(this_cpu);
+ struct sched_domain *sd;

for_each_domain(this_cpu, sd) {
if (!(sd->flags & SD_LOAD_BALANCE))
@@ -2893,6 +2898,9 @@ static inline void rebalance_tick(int cp
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)
@@ -3039,36 +3047,8 @@ void account_steal_time(struct task_stru
cpustat->steal = cputime64_add(cpustat->steal, tmp);
}

-/*
- * This function gets called by the timer code, with HZ frequency.
- * We call it with interrupts disabled.
- *
- * It also gets called by the fork code, when changing the parent's
- * timeslices.
- */
-void scheduler_tick(void)
+void time_slice(struct rq *rq, struct task_struct *p)
{
- unsigned long long now = sched_clock();
- struct task_struct *p = current;
- int cpu = smp_processor_id();
- struct rq *rq = cpu_rq(cpu);
-
- update_cpu_clock(p, rq, now);
-
- rq->timestamp_last_tick = now;
-
- if (p == rq->idle) {
- if (wake_priority_sleeper(rq))
- goto out;
- rebalance_tick(cpu, rq, SCHED_IDLE);
- return;
- }
-
- /* Task might have expired already, but not scheduled off yet */
- if (p->array != rq->active) {
- set_tsk_need_resched(p);
- goto out;
- }
spin_lock(&rq->lock);
/*
* The task was running during this tick - update the
@@ -3135,8 +3115,41 @@ void scheduler_tick(void)
}
out_unlock:
spin_unlock(&rq->lock);
-out:
- rebalance_tick(cpu, rq, NOT_IDLE);
+}
+
+/*
+ * This function gets called by the timer code, with HZ frequency.
+ * We call it with interrupts disabled.
+ *
+ * It also gets called by the fork code, when changing the parent's
+ * timeslices.
+ */
+void scheduler_tick(void)
+{
+ unsigned long long now = sched_clock();
+ 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) {
+ /* Task on the idle queue */
+ if (!wake_priority_sleeper(rq))
+ idle = SCHED_IDLE;
+ } else {
+ /* Task on cpu queue */
+ if (p->array != rq->active)
+ /* Task has expired but was not scheduled yet */
+ set_tsk_need_resched(p);
+ else
+ time_slice(rq, p);
+ }
+ update_load(rq);
+ rebalance_tick(cpu, rq, idle);
}

#ifdef CONFIG_SCHED_SMT
-
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