linux-kernel - [PATCH 07/16] sched: Make SD_BALANCE

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Date:	Mon, 23 May 2016 11:58:49 +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>
Subject: [PATCH 07/16] sched: Make SD_BALANCE_WAKE a topology flag

For systems with the SD_ASYM_CPUCAPACITY flag set on higher level in the
sched_domain hierarchy we need a way to enable wake-up balancing for the
lower levels as well as we may want to balance tasks that don't fit the
capacity of the previous cpu.

We have the option of introducing a new topology flag to express this
requirement, or let the existing SD_BALANCE_WAKE flag be set by the
architecture as a topology flag. The former means introducing yet
another flag, the latter breaks the current meaning of topology flags.
None of the options are really desirable.

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

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
 kernel/sched/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 558ec4a..8014b4a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5658,6 +5658,7 @@ static int sd_degenerate(struct sched_domain *sd)
 			 SD_BALANCE_NEWIDLE |
 			 SD_BALANCE_FORK |
 			 SD_BALANCE_EXEC |
+			 SD_BALANCE_WAKE |
 			 SD_SHARE_CPUCAPACITY |
 			 SD_ASYM_CPUCAPACITY |
 			 SD_SHARE_PKG_RESOURCES |
@@ -5690,6 +5691,7 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent)
 				SD_BALANCE_NEWIDLE |
 				SD_BALANCE_FORK |
 				SD_BALANCE_EXEC |
+				SD_BALANCE_WAKE |
 				SD_ASYM_CPUCAPACITY |
 				SD_SHARE_CPUCAPACITY |
 				SD_SHARE_PKG_RESOURCES |
@@ -6308,6 +6310,7 @@ static int sched_domains_curr_level;
  * Odd ones out:
  * SD_ASYM_PACKING        - describes SMT quirks
  * SD_ASYM_CPUCAPACITY    - describes mixed capacity topologies
+ * SD_BALANCE_WAKE	  - controls wake-up balancing (expensive)
  */
 #define TOPOLOGY_SD_FLAGS		\
 	(SD_SHARE_CPUCAPACITY |		\
@@ -6315,6 +6318,7 @@ static int sched_domains_curr_level;
 	 SD_NUMA |			\
 	 SD_ASYM_PACKING |		\
 	 SD_ASYM_CPUCAPACITY |		\
+	 SD_BALANCE_WAKE |		\
 	 SD_SHARE_POWERDOMAIN)
 
 static struct sched_domain *
-- 
1.9.1