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Subject[PATCH v3 5/7] sched/topology: Add more flags to the SD degeneration mask
Date
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.schneider@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 6047d491abe9..fe393b295444 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
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