sched: Extend active balance to accept 'push_task' argument

Active balance currently picks one task to migrate from busy cpu to
a chosen cpu (push_cpu). This patch extends active load balance to
recognize a particular task ('push_task') that needs to be migrated to
'push_cpu'. This capability will be leveraged by HMP-aware task
placement in a subsequent patch.

Change-Id: If31320111e6cc7044e617b5c3fd6d8e0c0e16952
Signed-off-by: Srivatsa Vaddagiri <vatsa@codeaurora.org>
[rameezmustafa@codeaurora.org]: Port to msm-3.18]
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 18d607f..679791f 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7909,6 +7909,7 @@ void __init sched_init(void)
                rq->active_balance = 0;
                rq->next_balance = jiffies;
                rq->push_cpu = 0;
+               rq->push_task = NULL;
                rq->cpu = i;
                rq->online = 0;
                rq->idle_stamp = 0;

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b904a02..716aa34 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9429,8 +9429,18 @@ static int active_load_balance_cpu_stop(void *data)
        int busiest_cpu = cpu_of(busiest_rq);
        int target_cpu = busiest_rq->push_cpu;
        struct rq *target_rq = cpu_rq(target_cpu);
-       struct sched_domain *sd;
+       struct sched_domain *sd = NULL;
        struct task_struct *p = NULL;
+       struct task_struct *push_task;
+       int push_task_detached = 0;
+       struct lb_env env = {
+               .sd             = sd,
+               .dst_cpu        = target_cpu,
+               .dst_rq         = target_rq,
+               .src_cpu        = busiest_rq->cpu,
+               .src_rq         = busiest_rq,
+               .idle           = CPU_IDLE,
+       };
 
        raw_spin_lock_irq(&busiest_rq->lock);
 
@@ -9450,6 +9460,16 @@ static int active_load_balance_cpu_stop(void *data)
         */
        BUG_ON(busiest_rq == target_rq);
 
+       push_task = busiest_rq->push_task;
+       if (push_task) {
+               if (task_on_rq_queued(push_task) &&
+                               task_cpu(push_task) == busiest_cpu) {
+                       detach_task(push_task, &env);
+                       push_task_detached = 1;
+               }
+               goto out_unlock;
+       }
+
        /* Search for an sd spanning us and the target CPU. */
        rcu_read_lock();
        for_each_domain(target_cpu, sd) {
@@ -9459,15 +9479,7 @@ static int active_load_balance_cpu_stop(void *data)
        }
 
        if (likely(sd)) {
-               struct lb_env env = {
-                       .sd             = sd,
-                       .dst_cpu        = target_cpu,
-                       .dst_rq         = target_rq,
-                       .src_cpu        = busiest_rq->cpu,
-                       .src_rq         = busiest_rq,
-                       .idle           = CPU_IDLE,
-               };
-
+               env.sd = sd;
                schedstat_inc(sd, alb_count);
                update_rq_clock(busiest_rq);
 
@@ -9485,8 +9497,18 @@ static int active_load_balance_cpu_stop(void *data)
        rcu_read_unlock();
 out_unlock:
        busiest_rq->active_balance = 0;
+
+       if (push_task)
+               busiest_rq->push_task = NULL;
+
        raw_spin_unlock(&busiest_rq->lock);
 
+       if (push_task) {
+               if (push_task_detached)
+                       attach_one_task(target_rq, push_task);
+               put_task_struct(push_task);
+       }
+
        if (p)
                attach_one_task(target_rq, p);
 

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index dd86072..af2fd9c 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -664,6 +664,7 @@ struct rq {
        /* For active balancing */
        int active_balance;
        int push_cpu;
+       struct task_struct *push_task;
        struct cpu_stop_work active_balance_work;
        /* cpu of this runqueue: */
        int cpu;