linux-kernel - [PATCH v5 09/17] sched/topology: Remove SD

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Date:   Wed, 12 Aug 2020 13:52:52 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>, mingo@...nel.org,
        vincent.guittot@...aro.org, morten.rasmussen@....com,
        Quentin Perret <qperret@...gle.com>
Subject: [PATCH v5 09/17] sched/topology: Remove SD_SERIALIZE degeneration special case

If there is only a single NUMA node in the system, the only NUMA topology
level that will be generated will be NODE (identity distance), which
doesn't have SD_SERIALIZE.

This means we don't need this special case in sd_parent_degenerate(), as
having the NODE level "naturally" covers it. Thus, remove it.

Suggested-by: Peter Zijlstra <peterz@...radead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
---
 kernel/sched/topology.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 5f2bc99ff659..00ad7cef2ec1 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -183,11 +183,9 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
 		return 0;
 
 	/* Flags needing groups don't count if only 1 group in parent */
-	if (parent->groups == parent->groups->next) {
+	if (parent->groups == parent->groups->next)
 		pflags &= ~(SD_DEGENERATE_GROUPS_MASK | SD_PREFER_SIBLING);
-		if (nr_node_ids == 1)
-			pflags &= ~SD_SERIALIZE;
-	}
+
 	if (~cflags & pflags)
 		return 0;
 
-- 
2.27.0