sched/core: 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.

Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: dietmar.eggemann@arm.com
Cc: freedom.tan@mediatek.com
Cc: keita.kobayashi.ym@renesas.com
Cc: mgalbraith@suse.de
Cc: sgurrappadi@nvidia.com
Cc: vincent.guittot@linaro.org
Cc: yuyang.du@intel.com
Link: http://lkml.kernel.org/r/1469453670-2660-8-git-send-email-morten.rasmussen@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 57394650c6ab27c313e994198662a320ab9d13fa..4695df6ed752d43f83318b5c69a9973d7604953d 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6444,6 +6444,13 @@ 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;