[PATCH] sched: fix SMT scheduler latency bug

[pandora-kernel.git] / kernel / sched.c

diff --git a/kernel/sched.c b/kernel/sched.c
index 6da13bb..c61ee34 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2650,6 +2650,16 @@ static inline void wake_sleeping_dependent(int this_cpu, runqueue_t *this_rq)
         */
 }
 
         */
 }
 

+/*
+ * number of 'lost' timeslices this task wont be able to fully
+ * utilize, if another task runs on a sibling. This models the
+ * slowdown effect of other tasks running on siblings:
+ */
+static inline unsigned long smt_slice(task_t *p, struct sched_domain *sd)
+{
+       return p->time_slice * (100 - sd->per_cpu_gain) / 100;
+}
+

 static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
 {
        struct sched_domain *tmp, *sd = NULL;
 static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
 {
        struct sched_domain *tmp, *sd = NULL;


@@ -2714,8 +2724,9 @@ static inline int dependent_sleeper(int this_cpu, runqueue_t *this_rq)
                                (sd->per_cpu_gain * DEF_TIMESLICE / 100))
                                        ret = 1;
                } else
                                (sd->per_cpu_gain * DEF_TIMESLICE / 100))
                                        ret = 1;
                } else

-                       if (((smt_curr->time_slice * (100 - sd->per_cpu_gain) /
-                               100) > task_timeslice(p)))
+                       if (smt_curr->static_prio < p->static_prio &&
+                               !TASK_PREEMPTS_CURR(p, smt_rq) &&
+                               smt_slice(smt_curr, sd) > task_timeslice(p))

                                        ret = 1;
 
 check_smt_task:
                                        ret = 1;
 
 check_smt_task:


@@ -2737,8 +2748,8 @@ check_smt_task:
                                (sd->per_cpu_gain * DEF_TIMESLICE / 100))
                                        resched_task(smt_curr);
                } else {
                                (sd->per_cpu_gain * DEF_TIMESLICE / 100))
                                        resched_task(smt_curr);
                } else {

-                       if ((p->time_slice * (100 - sd->per_cpu_gain) / 100) >
-                               task_timeslice(smt_curr))
+                       if (TASK_PREEMPTS_CURR(p, smt_rq) &&
+                               smt_slice(p, sd) > task_timeslice(smt_curr))

                                        resched_task(smt_curr);
                        else
                                wakeup_busy_runqueue(smt_rq);
                                        resched_task(smt_curr);
                        else
                                wakeup_busy_runqueue(smt_rq);