[RFC][PATCH 3/8] sched/fair: Add cgroup_mode: UP

[Peter Zijlstra <peterz@infradead.org>]

Instead of calculating the proportional fraction of tg->shares for
each CPU, just give each CPU the full measure, ignoring these pesky
SMP problems.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/sched/debug.c |    3 ++-
 kernel/sched/fair.c  |   19 ++++++++++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -588,9 +588,10 @@ static void debugfs_fair_server_init(voi
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
-int cgroup_mode = 0;
+int cgroup_mode = 1;
 
 static const char *cgroup_mode_str[] = {
+	"up",
 	"smp",
 };
 
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4152,7 +4152,7 @@ static inline int throttled_hierarchy(st
  *
  * hence icky!
  */
-static long calc_group_shares(struct cfs_rq *cfs_rq)
+static long calc_smp_shares(struct cfs_rq *cfs_rq)
 {
 	long tg_weight, tg_shares, load, shares;
 	struct task_group *tg = cfs_rq->tg;
@@ -4187,6 +4187,23 @@ static long calc_group_shares(struct cfs
 }
 
 /*
+ * Ignore this pesky SMP stuff, use (4).
+ */
+static long calc_up_shares(struct cfs_rq *cfs_rq)
+{
+	struct task_group *tg = cfs_rq->tg;
+	return READ_ONCE(tg->shares);
+}
+
+static long calc_group_shares(struct cfs_rq *cfs_rq)
+{
+	if (cgroup_mode == 0)
+		return calc_up_shares(cfs_rq);
+
+	return calc_smp_shares(cfs_rq);
+}
+
+/*
  * Recomputes the group entity based on the current state of its group
  * runqueue.
  */