linux-kernel - [PATCH v3 07/13] sched: Enable SD_BALANCE

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Message-Id: <1469453670-2660-8-git-send-email-morten.rasmussen@arm.com>
Date:	Mon, 25 Jul 2016 14:34:24 +0100
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	peterz@...radead.org, mingo@...hat.com
Cc:	dietmar.eggemann@....com, yuyang.du@...el.com,
	vincent.guittot@...aro.org, mgalbraith@...e.de,
	sgurrappadi@...dia.com, freedom.tan@...iatek.com,
	keita.kobayashi.ym@...esas.com, linux-kernel@...r.kernel.org,
	Morten Rasmussen <morten.rasmussen@....com>
Subject: [PATCH v3 07/13] sched: Enable SD_BALANCE_WAKE for asymmetric capacity systems

A domain with the SD_ASYM_CPUCAPACITY flag set indicate that
sched_groups at this level and below do not include cpus of all
capacities available (e.g. group containing little-only or big-only cpus
in big.LITTLE systems). It is therefore necessary to put in more effort
in finding an appropriate cpu at task wake-up by enabling balancing at
wake-up (SD_BALANCE_WAKE) on all lower (child) levels.

cc: Ingo Molnar <mingo@...hat.com>
cc: Peter Zijlstra <peterz@...radead.org>

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
 kernel/sched/core.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index ec3f7aef321f..a0a74b2d9f41 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6414,6 +6414,13 @@ sd_init(struct sched_domain_topology_level *tl,
 	 * Convert topological properties into behaviour.
 	 */
 
+	if (sd->flags & SD_ASYM_CPUCAPACITY) {
+		struct sched_domain *t = sd;
+
+		for_each_lower_domain(t)
+			t->flags |= SD_BALANCE_WAKE;
+	}
+
 	if (sd->flags & SD_SHARE_CPUCAPACITY) {
 		sd->flags |= SD_PREFER_SIBLING;
 		sd->imbalance_pct = 110;
-- 
1.9.1