linux-kernel - [PATCH 15/16] arm: Set SD_BALANCE_WAKE flag for asymmetric capacity systems

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Date:	Mon, 23 May 2016 11:58:57 +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,
	linux-kernel@...r.kernel.org,
	Morten Rasmussen <morten.rasmussen@....com>,
	Russell King <linux@....linux.org.uk>
Subject: [PATCH 15/16] arm: Set SD_BALANCE_WAKE flag for asymmetric capacity systems

Asymmetric capacity systems (e.g. ARM big.LITTLE) can not rely
exclusively on fast idle-based task placement at wake-up in all
scenarios. Enable SD_BALANCE_WAKE to have the option to do
load/utilization based wake-up task placement (existing tasks) if affine
wake-up fails.

cc: Russell King <linux@....linux.org.uk>

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
 arch/arm/kernel/topology.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/arm/kernel/topology.c b/arch/arm/kernel/topology.c
index 1b81b31..32d0a1b 100644
--- a/arch/arm/kernel/topology.c
+++ b/arch/arm/kernel/topology.c
@@ -280,18 +280,27 @@ void store_cpu_topology(unsigned int cpuid)
 
 static inline int cpu_corepower_flags(void)
 {
-	return SD_SHARE_PKG_RESOURCES  | SD_SHARE_POWERDOMAIN;
+	int flags = SD_SHARE_PKG_RESOURCES  | SD_SHARE_POWERDOMAIN;
+
+	return big_little ? flags | SD_BALANCE_WAKE : flags;
+}
+
+static inline int arm_cpu_core_flags(void)
+{
+	int flags = SD_SHARE_PKG_RESOURCES;
+
+	return big_little ? flags | SD_BALANCE_WAKE : flags;
 }
 
 static inline int arm_cpu_cpu_flags(void)
 {
-	return big_little ? SD_ASYM_CPUCAPACITY : 0;
+	return big_little ? SD_ASYM_CPUCAPACITY | SD_BALANCE_WAKE : 0;
 }
 
 static struct sched_domain_topology_level arm_topology[] = {
 #ifdef CONFIG_SCHED_MC
 	{ cpu_corepower_mask, cpu_corepower_flags, SD_INIT_NAME(GMC) },
-	{ cpu_coregroup_mask, cpu_core_flags, SD_INIT_NAME(MC) },
+	{ cpu_coregroup_mask, arm_cpu_core_flags, SD_INIT_NAME(MC) },
 #endif
 	{ cpu_cpu_mask, arm_cpu_cpu_flags, SD_INIT_NAME(DIE) },
 	{ NULL, },
-- 
1.9.1