sched: Rate-limit newidle

Rate limit newidle to migration_cost. It's a win for all
stages of sysbench oltp tests.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 25 insertions, 1 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index ae026aad145b..f8492123b5d1 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -589,6 +589,8 @@ struct rq {
 
         u64 rt_avg;
         u64 age_stamp;
+        u64 idle_stamp;
+        u64 avg_idle;
 #endif
 
         /* calc_load related fields */
@@ -2353,6 +2355,17 @@ static int try_to_wake_up(struct task_struct *p, unsigned int state,
         if (rq != orig_rq)
                 update_rq_clock(rq);
 
+        if (rq->idle_stamp) {
+                u64 delta = rq->clock - rq->idle_stamp;
+                u64 max = 2*sysctl_sched_migration_cost;
+
+                if (delta > max)
+                        rq->avg_idle = max;
+                else
+                        update_avg(&rq->avg_idle, delta);
+                rq->idle_stamp = 0;
+        }
+
         WARN_ON(p->state != TASK_WAKING);
         cpu = task_cpu(p);
 
@@ -4389,6 +4402,11 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
         int pulled_task = 0;
         unsigned long next_balance = jiffies + HZ;
 
+        this_rq->idle_stamp = this_rq->clock;
+
+        if (this_rq->avg_idle < sysctl_sched_migration_cost)
+                return;
+
         for_each_domain(this_cpu, sd) {
                 unsigned long interval;
 
@@ -4403,8 +4421,10 @@ static void idle_balance(int this_cpu, struct rq *this_rq)
                 interval = msecs_to_jiffies(sd->balance_interval);
                 if (time_after(next_balance, sd->last_balance + interval))
                         next_balance = sd->last_balance + interval;
-                if (pulled_task)
+                if (pulled_task) {
+                        this_rq->idle_stamp = 0;
                         break;
+                }
         }
         if (pulled_task || time_after(jiffies, this_rq->next_balance)) {
                 /*
diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index efb84409bc43..6988cf08f705 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -285,12 +285,16 @@ static void print_cpu(struct seq_file *m, int cpu)
 
 #ifdef CONFIG_SCHEDSTATS
 #define P(n) SEQ_printf(m, "  .%-30s: %d\n", #n, rq->n);
+#define P64(n) SEQ_printf(m, "  .%-30s: %Ld\n", #n, rq->n);
 
         P(yld_count);
 
         P(sched_switch);
         P(sched_count);
         P(sched_goidle);
+#ifdef CONFIG_SMP
+        P64(avg_idle);
+#endif
 
         P(ttwu_count);
         P(ttwu_local);