Merge git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched

* git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched:
  sched: clean up task_new_fair()
  sched: small schedstat fix
  sched: fix wait_start_fair condition in update_stats_wait_end()
  sched: call update_curr() in task_tick_fair()
  sched: make the scheduler converge to the ideal latency
  sched: fix sleeper bonus limit

2 files changed, 36 insertions, 11 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 9fe473a190de..b533d6db78aa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1587,6 +1587,7 @@ static void __sched_fork(struct task_struct *p)
         p->se.wait_start_fair           = 0;
         p->se.exec_start                = 0;
         p->se.sum_exec_runtime          = 0;
+        p->se.prev_sum_exec_runtime     = 0;
         p->se.delta_exec                = 0;
         p->se.delta_fair_run            = 0;
         p->se.delta_fair_sleep          = 0;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ee3771850aaf..ce39282d9c0d 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -354,7 +354,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr)
         delta_fair = calc_delta_fair(delta_exec, lw);
         delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
 
-        if (cfs_rq->sleeper_bonus > sysctl_sched_latency) {
+        if (cfs_rq->sleeper_bonus > sysctl_sched_min_granularity) {
                 delta = min((u64)delta_mine, cfs_rq->sleeper_bonus);
                 delta = min(delta, (unsigned long)(
                         (long)sysctl_sched_runtime_limit - curr->wait_runtime));
@@ -489,6 +489,9 @@ update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
         unsigned long delta_fair;
 
+        if (unlikely(!se->wait_start_fair))
+                return;
+
         delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
                         (u64)(cfs_rq->fair_clock - se->wait_start_fair));
 
@@ -668,7 +671,7 @@ dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
 /*
  * Preempt the current task with a newly woken task if needed:
  */
-static void
+static int
 __check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
                           struct sched_entity *curr, unsigned long granularity)
 {
@@ -679,8 +682,11 @@ __check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
          * preempt the current task unless the best task has
          * a larger than sched_granularity fairness advantage:
          */
-        if (__delta > niced_granularity(curr, granularity))
+        if (__delta > niced_granularity(curr, granularity)) {
                 resched_task(rq_of(cfs_rq)->curr);
+                return 1;
+        }
+        return 0;
 }
 
 static inline void
@@ -725,6 +731,7 @@ static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
 
 static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
 {
+        unsigned long gran, ideal_runtime, delta_exec;
         struct sched_entity *next;
 
         /*
@@ -741,8 +748,22 @@ static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
         if (next == curr)
                 return;
 
-        __check_preempt_curr_fair(cfs_rq, next, curr,
-                        sched_granularity(cfs_rq));
+        gran = sched_granularity(cfs_rq);
+        ideal_runtime = niced_granularity(curr,
+                max(sysctl_sched_latency / cfs_rq->nr_running,
+                    (unsigned long)sysctl_sched_min_granularity));
+        /*
+         * If we executed more than what the latency constraint suggests,
+         * reduce the rescheduling granularity. This way the total latency
+         * of how much a task is not scheduled converges to
+         * sysctl_sched_latency:
+         */
+        delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
+        if (delta_exec > ideal_runtime)
+                gran = 0;
+
+        if (__check_preempt_curr_fair(cfs_rq, next, curr, gran))
+                curr->prev_sum_exec_runtime = curr->sum_exec_runtime;
 }
 
 /**************************************************
@@ -1076,31 +1097,34 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr)
 static void task_new_fair(struct rq *rq, struct task_struct *p)
 {
         struct cfs_rq *cfs_rq = task_cfs_rq(p);
-        struct sched_entity *se = &p->se;
+        struct sched_entity *se = &p->se, *curr = cfs_rq_curr(cfs_rq);
 
         sched_info_queued(p);
 
+        update_curr(cfs_rq);
         update_stats_enqueue(cfs_rq, se);
         /*
          * Child runs first: we let it run before the parent
          * until it reschedules once. We set up the key so that
          * it will preempt the parent:
          */
-        p->se.fair_key = current->se.fair_key -
-                niced_granularity(&rq->curr->se, sched_granularity(cfs_rq)) - 1;
+        se->fair_key = curr->fair_key -
+                niced_granularity(curr, sched_granularity(cfs_rq)) - 1;
         /*
          * The first wait is dominated by the child-runs-first logic,
          * so do not credit it with that waiting time yet:
          */
         if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL)
-                p->se.wait_start_fair = 0;
+                se->wait_start_fair = 0;
 
         /*
          * The statistical average of wait_runtime is about
          * -granularity/2, so initialize the task with that:
          */
-        if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
-                p->se.wait_runtime = -(sched_granularity(cfs_rq) / 2);
+        if (sysctl_sched_features & SCHED_FEAT_START_DEBIT) {
+                se->wait_runtime = -(sched_granularity(cfs_rq) / 2);
+                schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
+        }
 
         __enqueue_entity(cfs_rq, se);
 }