[PATCH v4 07/10] sched/topology: Add more flags to the SD degeneration mask

[Valentin Schneider]

I don't think it is going to change much in practice, but we were missing
those:

o SD_BALANCE_WAKE: Used just like the other SD_BALANCE_* flags, so also
  needs > 1 group.
o SD_ASYM_PACKING: Hinges on load balancing (periodic / wakeup), thus needs
  > 1 group to happen
o SD_OVERLAP: Describes domains with overlapping groups; can't have
  overlaps with a single group.

SD_PREFER_SIBLING is as always the odd one out: we currently consider it
in sd_parent_degenerate() but not in sd_degenerate(). It too hinges on load
balancing, and thus won't have any effect when set on a domain with a
single group. Add it to the sd_degenerate() groups mask.

Signed-off-by: Valentin Schneider <valentin.schnei...@arm.com>
---
 kernel/sched/topology.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index cda02507aebf..93a7ff52335b 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -161,11 +161,15 @@ static int sd_degenerate(struct sched_domain *sd)
 
        /* Following flags need at least 2 groups */
        if (sd->flags & (SD_BALANCE_NEWIDLE |
+                        SD_BALANCE_WAKE |
                         SD_BALANCE_FORK |
                         SD_BALANCE_EXEC |
+                        SD_ASYM_PACKING |
                         SD_SHARE_CPUCAPACITY |
                         SD_ASYM_CPUCAPACITY |
-                        SD_SHARE_PKG_RESOURCES)) {
+                        SD_SHARE_PKG_RESOURCES |
+                        SD_OVERLAP |
+                        SD_PREFER_SIBLING)) {
                if (sd->groups != sd->groups->next)
                        return 0;
        }
@@ -191,11 +195,14 @@ sd_parent_degenerate(struct sched_domain *sd, struct 
sched_domain *parent)
        /* Flags needing groups don't count if only 1 group in parent */
        if (parent->groups == parent->groups->next) {
                pflags &= ~(SD_BALANCE_NEWIDLE |
+                           SD_BALANCE_WAKE |
                            SD_BALANCE_FORK |
                            SD_BALANCE_EXEC |
+                           SD_ASYM_PACKING |
                            SD_ASYM_CPUCAPACITY |
                            SD_SHARE_CPUCAPACITY |
                            SD_SHARE_PKG_RESOURCES |
+                           SD_OVERLAP |
                            SD_PREFER_SIBLING);
                if (nr_node_ids == 1)
                        pflags &= ~SD_SERIALIZE;
-- 
2.27.0