sched: incremental effective_load()

Increase the accuracy of the effective_load values.

Not only consider the current increment (as per the attempted wakeup), but
also consider the delta between when we last adjusted the shares and the
current situation.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 21 insertions, 3 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 01d3e51b7116..7613f69f0978 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -427,6 +427,11 @@ struct cfs_rq {
          * this cpu's part of tg->shares
          */
         unsigned long shares;
+
+        /*
+         * load.weight at the time we set shares
+         */
+        unsigned long rq_weight;
 #endif
 #endif
 };
@@ -1527,6 +1532,7 @@ __update_group_shares_cpu(struct task_group *tg, int cpu,
          * record the actual number of shares, not the boosted amount.
          */
         tg->cfs_rq[cpu]->shares = boost ? 0 : shares;
+        tg->cfs_rq[cpu]->rq_weight = rq_weight;
 
         if (shares < MIN_SHARES)
                 shares = MIN_SHARES;
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index bed2f71e63d9..e87f1a52f625 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -1074,10 +1074,22 @@ static inline int wake_idle(int cpu, struct task_struct *p)
 static const struct sched_class fair_sched_class;
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-static unsigned long effective_load(struct task_group *tg, int cpu,
-                unsigned long wl, unsigned long wg)
+static long effective_load(struct task_group *tg, int cpu,
+                long wl, long wg)
 {
         struct sched_entity *se = tg->se[cpu];
+        long more_w;
+
+        if (!tg->parent)
+                return wl;
+
+        /*
+         * Instead of using this increment, also add the difference
+         * between when the shares were last updated and now.
+         */
+        more_w = se->my_q->load.weight - se->my_q->rq_weight;
+        wl += more_w;
+        wg += more_w;
 
         for_each_sched_entity(se) {
 #define D(n) (likely(n) ? (n) : 1)
@@ -1086,7 +1098,7 @@ static unsigned long effective_load(struct task_group *tg, int cpu,
 
                 S = se->my_q->tg->shares;
                 s = se->my_q->shares;
-                rw = se->my_q->load.weight;
+                rw = se->my_q->rq_weight;
 
                 a = S*(rw + wl);
                 b = S*rw + s*wg;