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

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Date:   Thu, 20 Feb 2020 20:09:12 -0000
From:   "tip-bot2 for Morten Rasmussen" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Morten Rasmussen <morten.rasmussen@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Quentin Perret <qperret@...gle.com>, x86 <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [tip: sched/core] sched/topology: Remove SD_BALANCE_WAKE on
 asymmetric capacity systems

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

Commit-ID:     a526d466798d65cff120ee00ef92931075bf3769
Gitweb:        https://git.kernel.org/tip/a526d466798d65cff120ee00ef92931075bf3769
Author:        Morten Rasmussen <morten.rasmussen@....com>
AuthorDate:    Thu, 06 Feb 2020 19:19:55 
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 20 Feb 2020 21:03:14 +01:00

sched/topology: Remove SD_BALANCE_WAKE on asymmetric capacity systems

SD_BALANCE_WAKE was previously added to lower sched_domain levels on
asymmetric CPU capacity systems by commit:

  9ee1cda5ee25 ("sched/core: Enable SD_BALANCE_WAKE for asymmetric capacity systems")

to enable the use of find_idlest_cpu() and friends to find an appropriate
CPU for tasks.

That responsibility has now been shifted to select_idle_sibling() and
friends, and hence the flag can be removed. Note that this causes
asymmetric CPU capacity systems to no longer enter the slow wakeup path
(find_idlest_cpu()) on wakeups - only on execs and forks (which is aligned
with all other mainline topologies).

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
[Changelog tweaks]
Signed-off-by: Valentin Schneider <valentin.schneider@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Quentin Perret <qperret@...gle.com>
Link: https://lkml.kernel.org/r/20200206191957.12325-3-valentin.schneider@arm.com

---
 kernel/sched/topology.c | 15 +++------------
 1 file changed, 3 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index dfb64c0..0091188 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -1374,18 +1374,9 @@ sd_init(struct sched_domain_topology_level *tl,
 	 * Convert topological properties into behaviour.
 	 */
 
-	if (sd->flags & SD_ASYM_CPUCAPACITY) {
-		struct sched_domain *t = sd;
-
-		/*
-		 * Don't attempt to spread across CPUs of different capacities.
-		 */
-		if (sd->child)
-			sd->child->flags &= ~SD_PREFER_SIBLING;
-
-		for_each_lower_domain(t)
-			t->flags |= SD_BALANCE_WAKE;
-	}
+	/* Don't attempt to spread across CPUs of different capacities. */
+	if ((sd->flags & SD_ASYM_CPUCAPACITY) && sd->child)
+		sd->child->flags &= ~SD_PREFER_SIBLING;
 
 	if (sd->flags & SD_SHARE_CPUCAPACITY) {
 		sd->imbalance_pct = 110;