sched: dont micro manage share losses

We used to try and contain the loss of 'shares' by playing arithmetic
games. Replace that by noticing that at the top sched_domain we'll
always have the full weight in shares to distribute.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 3 insertions, 23 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index dae20199dc9c..28229c5d4983 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -1551,6 +1551,9 @@ aggregate_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
         if ((!shares && aggregate(tg, cpu)->rq_weight) || shares > tg->shares)
                 shares = tg->shares;
 
+        if (!sd->parent || !(sd->parent->flags & SD_LOAD_BALANCE))
+                shares = tg->shares;
+
         aggregate(tg, cpu)->shares = shares;
 }
 
@@ -1642,20 +1645,8 @@ static void
 __move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
                     int scpu, int dcpu)
 {
-        unsigned long shares;
-
-        shares = tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
-
         __update_group_shares_cpu(tg, cpu, sd, scpu);
         __update_group_shares_cpu(tg, cpu, sd, dcpu);
-
-        /*
-         * ensure we never loose shares due to rounding errors in the
-         * above redistribution.
-         */
-        shares -= tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;
-        if (shares)
-                tg->cfs_rq[dcpu]->shares += shares;
 }
 
 /*
@@ -1675,7 +1666,6 @@ move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
 static void
 aggregate_group_set_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
 {
-        unsigned long shares = aggregate(tg, cpu)->shares;
         int i;
 
         for_each_cpu_mask(i, sd->span) {
@@ -1688,16 +1678,6 @@ aggregate_group_set_shares(struct task_group *tg, int cpu, struct sched_domain *
         }
 
         aggregate_group_shares(tg, cpu, sd);
-
-        /*
-         * ensure we never loose shares due to rounding errors in the
-         * above redistribution.
-         */
-        shares -= aggregate(tg, cpu)->shares;
-        if (shares) {
-                tg->cfs_rq[cpu]->shares += shares;
-                aggregate(tg, cpu)->shares += shares;
-        }
 }
 
 /*