Commit-ID: facc28ddd17e2eb4f4fed4ea5fc30b6cda83c409
Gitweb: https://git.kernel.org/tip/facc28ddd17e2eb4f4fed4ea5fc30b6cda83c409
Author: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
AuthorDate: Fri, 14 Dec 2018 17:01:57 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 21 Jan 2019 14:43:25 +0100
sched/fair: Fix unnecessary increase of balance interval
In case of active balancing, we increase the balance interval to cover
pinned tasks cases not covered by all_pinned logic. Neverthless, the
active migration triggered by asym packing should be treated as the normal
unbalanced case and reset the interval to default value, otherwise active
migration for asym_packing can be easily delayed for hundreds of ms
because of this pinned task detection mechanism.
The same happens to other conditions tested in need_active_balance() like
misfit task and when the capacity of src_cpu is reduced compared to
dst_cpu (see comments in need_active_balance() for details).
Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: valentin.schneider@xxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
kernel/sched/fair.c | 40 +++++++++++++++++++++++++++-------------
1 file changed, 27 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 30450901200e..e2ff4b69dcf6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8826,21 +8826,25 @@ static struct rq *find_busiest_queue(struct lb_env *env,
*/
#define MAX_PINNED_INTERVAL 512
-static int need_active_balance(struct lb_env *env)
+static inline bool
+asym_active_balance(struct lb_env *env)
{
- struct sched_domain *sd = env->sd;
+ /*
+ * ASYM_PACKING needs to force migrate tasks from busy but
+ * lower priority CPUs in order to pack all tasks in the
+ * highest priority CPUs.
+ */
+ return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
+ sched_asym_prefer(env->dst_cpu, env->src_cpu);
+}
- if (env->idle != CPU_NOT_IDLE) {
+static inline bool
+voluntary_active_balance(struct lb_env *env)
+{
+ struct sched_domain *sd = env->sd;
- /*
- * ASYM_PACKING needs to force migrate tasks from busy but
- * lower priority CPUs in order to pack all tasks in the
- * highest priority CPUs.
- */
- if ((sd->flags & SD_ASYM_PACKING) &&
- sched_asym_prefer(env->dst_cpu, env->src_cpu))
- return 1;
- }
+ if (asym_active_balance(env))
+ return 1;
/*
* The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
@@ -8858,6 +8862,16 @@ static int need_active_balance(struct lb_env *env)
if (env->src_grp_type == group_misfit_task)
return 1;
+ return 0;
+}
+
+static int need_active_balance(struct lb_env *env)
+{
+ struct sched_domain *sd = env->sd;
+
+ if (voluntary_active_balance(env))
+ return 1;
+
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}
@@ -9119,7 +9133,7 @@ more_balance:
} else
sd->nr_balance_failed = 0;
- if (likely(!active_balance)) {
+ if (likely(!active_balance) || voluntary_active_balance(&env)) {
/* We were unbalanced, so reset the balancing interval */
sd->balance_interval = sd->min_interval;
} else {
|