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

diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index dfb64c0..0091188 100644 (file)
--- 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;