linux-kernel - [PATCH v3 5/7] sched/topology: Add more flags to the SD degeneration mask

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Message-Id: <20200701190656.10126-6-valentin.schneider@arm.com>
Date:   Wed,  1 Jul 2020 20:06:53 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, morten.rasmussen@....com
Subject: [PATCH v3 5/7] sched/topology: Add more flags to the SD degeneration mask

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@....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