linux-kernel - [tip: sched/core] sched/topology: Remove SD

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Date:   Wed, 19 Aug 2020 14:02:46 -0000
From:   "tip-bot2 for Valentin Schneider" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Ingo Molnar <mingo@...nel.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] sched/topology: Remove SD_SERIALIZE degeneration
 special case

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     ab65afb094c7b2e954e8d56ffbc7df843211c2c8
Gitweb:        https://git.kernel.org/tip/ab65afb094c7b2e954e8d56ffbc7df843211c2c8
Author:        Valentin Schneider <valentin.schneider@....com>
AuthorDate:    Mon, 17 Aug 2020 12:29:55 +01:00
Committer:     Ingo Molnar <mingo@...nel.org>
CommitterDate: Wed, 19 Aug 2020 10:49:48 +02:00

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>
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>
Acked-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Link: https://lore.kernel.org/r/20200817113003.20802-10-valentin.schneider@arm.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 38e6671..c662c53 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;