nfsd: filter readdir results in V4ROOT case

[safe/jmp/linux-2.6] / kernel / sched_fair.c

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c32c3e6..37087a7 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -822,6 +822,26 @@ check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
                 * re-elected due to buddy favours.
                 */
                clear_buddies(cfs_rq, curr);
+               return;
+       }
+
+       /*
+        * Ensure that a task that missed wakeup preemption by a
+        * narrow margin doesn't have to wait for a full slice.
+        * This also mitigates buddy induced latencies under load.
+        */
+       if (!sched_feat(WAKEUP_PREEMPT))
+               return;
+
+       if (delta_exec < sysctl_sched_min_granularity)
+               return;
+
+       if (cfs_rq->nr_running > 1) {
+               struct sched_entity *se = __pick_next_entity(cfs_rq);
+               s64 delta = curr->vruntime - se->vruntime;
+
+               if (delta > ideal_runtime)
+                       resched_task(rq_of(cfs_rq)->curr);
        }
 }
 
@@ -861,21 +881,18 @@ wakeup_preempt_entity(struct sched_entity *curr, struct sched_entity *se);
 static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
 {
        struct sched_entity *se = __pick_next_entity(cfs_rq);
-       struct sched_entity *buddy;
+       struct sched_entity *left = se;
 
-       if (cfs_rq->next) {
-               buddy = cfs_rq->next;
-               cfs_rq->next = NULL;
-               if (wakeup_preempt_entity(buddy, se) < 1)
-                       return buddy;
-       }
+       if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
+               se = cfs_rq->next;
 
-       if (cfs_rq->last) {
-               buddy = cfs_rq->last;
-               cfs_rq->last = NULL;
-               if (wakeup_preempt_entity(buddy, se) < 1)
-                       return buddy;
-       }
+       /*
+        * Prefer last buddy, try to return the CPU to a preempted task.
+        */
+       if (cfs_rq->last && wakeup_preempt_entity(cfs_rq->last, left) < 1)
+               se = cfs_rq->last;
+
+       clear_buddies(cfs_rq, se);
 
        return se;
 }
@@ -1577,6 +1594,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
        struct sched_entity *se = &curr->se, *pse = &p->se;
        struct cfs_rq *cfs_rq = task_cfs_rq(curr);
        int sync = wake_flags & WF_SYNC;
+       int scale = cfs_rq->nr_running >= sched_nr_latency;
 
        update_curr(cfs_rq);
 
@@ -1591,18 +1609,7 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
        if (unlikely(se == pse))
                return;
 
-       /*
-        * Only set the backward buddy when the current task is still on the
-        * rq. This can happen when a wakeup gets interleaved with schedule on
-        * the ->pre_schedule() or idle_balance() point, either of which can
-        * drop the rq lock.
-        *
-        * Also, during early boot the idle thread is in the fair class, for
-        * obvious reasons its a bad idea to schedule back to the idle thread.
-        */
-       if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
-               set_last_buddy(se);
-       if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
+       if (sched_feat(NEXT_BUDDY) && scale && !(wake_flags & WF_FORK))
                set_next_buddy(pse);
 
        /*
@@ -1648,8 +1655,22 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 
        BUG_ON(!pse);
 
-       if (wakeup_preempt_entity(se, pse) == 1)
+       if (wakeup_preempt_entity(se, pse) == 1) {
                resched_task(curr);
+               /*
+                * Only set the backward buddy when the current task is still
+                * on the rq. This can happen when a wakeup gets interleaved
+                * with schedule on the ->pre_schedule() or idle_balance()
+                * point, either of which can * drop the rq lock.
+                *
+                * Also, during early boot the idle thread is in the fair class,
+                * for obvious reasons its a bad idea to schedule back to it.
+                */
+               if (unlikely(!se->on_rq || curr == rq->idle))
+                       return;
+               if (sched_feat(LAST_BUDDY) && scale && entity_is_task(se))
+                       set_last_buddy(se);
+       }
 }
 
 static struct task_struct *pick_next_task_fair(struct rq *rq)