sched: group scheduling, change how cpu load is calculated

This patch changes how the cpu load exerted by fair_sched_class tasks
is calculated. Load exerted by fair_sched_class tasks on a cpu is now
a summation of the group weights, rather than summation of task weights.
Weight exerted by a group on a cpu is dependent on the shares allocated
to it.

This version of patch has a minor impact on code size, but should have
no runtime/functional impact for !CONFIG_FAIR_GROUP_SCHED.

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 27 insertions, 4 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index 0c5fdce67228..30ae9c2a2861 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -760,15 +760,26 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
 static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
 {
         struct cfs_rq *cfs_rq;
-        struct sched_entity *se = &p->se;
+        struct sched_entity *se = &p->se,
+                            *topse = NULL;      /* Highest schedulable entity */
+        int incload = 1;
 
         for_each_sched_entity(se) {
-                if (se->on_rq)
+                topse = se;
+                if (se->on_rq) {
+                        incload = 0;
                         break;
+                }
                 cfs_rq = cfs_rq_of(se);
                 enqueue_entity(cfs_rq, se, wakeup);
                 wakeup = 1;
         }
+        /* Increment cpu load if we just enqueued the first task of a group on
+         * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs
+         * at the highest grouping level.
+         */
+        if (incload)
+                inc_cpu_load(rq, topse->load.weight);
 }
 
 /*
@@ -779,16 +790,28 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
 static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
 {
         struct cfs_rq *cfs_rq;
-        struct sched_entity *se = &p->se;
+        struct sched_entity *se = &p->se,
+                            *topse = NULL;      /* Highest schedulable entity */
+        int decload = 1;
 
         for_each_sched_entity(se) {
+                topse = se;
                 cfs_rq = cfs_rq_of(se);
                 dequeue_entity(cfs_rq, se, sleep);
                 /* Don't dequeue parent if it has other entities besides us */
-                if (cfs_rq->load.weight)
+                if (cfs_rq->load.weight) {
+                        if (parent_entity(se))
+                                decload = 0;
                         break;
+                }
                 sleep = 1;
         }
+        /* Decrement cpu load if we just dequeued the last task of a group on
+         * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs
+         * at the highest grouping level.
+         */
+        if (decload)
+                dec_cpu_load(rq, topse->load.weight);
 }
 
 /*