[PATCH v7 09/14] sched/fair: Clean-up update_sg_lb_stats parameters

Quentin Perret
2018-09-12T09:14:03Z

In preparation for the introduction of a new root domain flag which can
be set during load balance (the 'overutilized' flag), clean-up the set
of parameters passed to update_sg_lb_stats(). More specifically, the
'local_group' and 'local_idx' parameters can be removed since they can
easily be reconstructed from within the function.

While at it, transform the 'overload' parameter into a flag stored in
the 'sg_status' parameter hence facilitating the definition of new flags
when needed.

Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Peter Zijlstra <peterz@infradead.org>
Suggested-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
---
kernel/sched/fair.c | 27 +++++++++++----------------
kernel/sched/sched.h | 3 +++
2 files changed, 14 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c28c7adcc7b3..23381feae4ec 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7782,16 +7782,16 @@ static bool update_nohz_stats(struct rq *rq, bool force)
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
* @group: sched_group whose statistics are to be updated.
- * @load_idx: Load index of sched_domain of this_cpu for load calc.
- * @local_group: Does group contain this_cpu.
* @sgs: variable to hold the statistics for this group.
- * @overload: Indicate pullable load (e.g. >1 runnable task).
+ * @sg_status: Holds flag indicating the status of the sched_group
*/
static inline void update_sg_lb_stats(struct lb_env *env,
- struct sched_group *group, int load_idx,
- int local_group, struct sg_lb_stats *sgs,
- bool *overload)
+ struct sched_group *group,
+ struct sg_lb_stats *sgs,
+ int *sg_status)
{
+ int local_group = cpumask_test_cpu(env->dst_cpu, sched_group_span(group));
+ int load_idx = get_sd_load_idx(env->sd, env->idle);
unsigned long load;
int i, nr_running;

@@ -7815,7 +7815,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,

nr_running = rq->nr_running;
if (nr_running > 1)
- *overload = true;
+ *sg_status |= SG_OVERLOAD;

#ifdef CONFIG_NUMA_BALANCING
sgs->nr_numa_running += rq->nr_numa_running;
@@ -7831,7 +7831,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
if (env->sd->flags & SD_ASYM_CPUCAPACITY &&
sgs->group_misfit_task_load < rq->misfit_task_load) {
sgs->group_misfit_task_load = rq->misfit_task_load;
- *overload = 1;
+ *sg_status |= SG_OVERLOAD;
}
}

@@ -7976,17 +7976,14 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
struct sched_group *sg = env->sd->groups;
struct sg_lb_stats *local = &sds->local_stat;
struct sg_lb_stats tmp_sgs;
- int load_idx;
- bool overload = false;
bool prefer_sibling = child && child->flags & SD_PREFER_SIBLING;
+ int sg_status = 0;

#ifdef CONFIG_NO_HZ_COMMON
if (env->idle == CPU_NEWLY_IDLE && READ_ONCE(nohz.has_blocked))
env->flags |= LBF_NOHZ_STATS;
#endif

- load_idx = get_sd_load_idx(env->sd, env->idle);
-
do {
struct sg_lb_stats *sgs = &tmp_sgs;
int local_group;
@@ -8001,8 +7998,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
update_group_capacity(env->sd, env->dst_cpu);
}

- update_sg_lb_stats(env, sg, load_idx, local_group, sgs,
- &overload);
+ update_sg_lb_stats(env, sg, sgs, &sg_status);

if (local_group)
goto next_group;
@@ -8052,8 +8048,7 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd

if (!env->sd->parent) {
/* update overload indicator if we are at root domain */
- if (READ_ONCE(env->dst_rq->rd->overload) != overload)
- WRITE_ONCE(env->dst_rq->rd->overload, overload);
+ WRITE_ONCE(env->dst_rq->rd->overload, sg_status & SG_OVERLOAD);
}
}

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 7ced27701454..bee902d46d35 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -707,6 +707,9 @@ struct perf_domain {
struct rcu_head rcu;
};

+/* Scheduling group status flags */
+#define SG_OVERLOAD 0x1 /* More than one runnable task on a CPU. */
+
/*
* We add the notion of a root-domain which will be used to define per-domain
* variables. Each exclusive cpuset essentially defines an island domain by
--
2.18.0