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Subject[RFC PATCH 5/5] sched: Update blocked load from NEWIDLE

Suggested-by: Brendan Jackman <brendan.jackman@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/core.c | 1 +
kernel/sched/fair.c | 47 +++++++++++++++++++++++++++++++++++++++++------
kernel/sched/sched.h | 1 +
3 files changed, 43 insertions(+), 6 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6002,6 +6002,7 @@ void __init sched_init(void)
rq_attach_root(rq, &def_root_domain);
#ifdef CONFIG_NO_HZ_COMMON
rq->last_load_update_tick = jiffies;
+ rq->last_blocked_load_update_tick = jiffies;
atomic_set(&rq->nohz_flags, 0);
#endif
#ifdef CONFIG_NO_HZ_FULL
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5379,6 +5379,14 @@ decay_load_missed(unsigned long load, un
}
return load;
}
+
+static struct {
+ cpumask_var_t idle_cpus_mask;
+ atomic_t nr_cpus;
+ unsigned long next_balance; /* in jiffy units */
+ unsigned long next_stats;
+} nohz ____cacheline_aligned;
+
#endif /* CONFIG_NO_HZ_COMMON */

/**
@@ -6942,6 +6950,7 @@ enum fbq_type { regular, remote, all };
#define LBF_NEED_BREAK 0x02
#define LBF_DST_PINNED 0x04
#define LBF_SOME_PINNED 0x08
+#define LBF_NOHZ_STATS 0x10

struct lb_env {
struct sched_domain *sd;
@@ -7380,6 +7389,10 @@ static void update_blocked_averages(int
if (cfs_rq_is_decayed(cfs_rq))
list_del_leaf_cfs_rq(cfs_rq);
}
+
+#ifdef CONFIG_NO_HZ_COMMON
+ rq->last_blocked_load_update_tick = jiffies;
+#endif
rq_unlock_irqrestore(rq, &rf);
}

@@ -7439,6 +7452,9 @@ static inline void update_blocked_averag
rq_lock_irqsave(rq, &rf);
update_rq_clock(rq);
update_cfs_rq_load_avg(cfs_rq_clock_task(cfs_rq), cfs_rq);
+#ifdef CONFIG_NO_HZ_COMMON
+ rq->last_blocked_load_update_tick = jiffies;
+#endif
rq_unlock_irqrestore(rq, &rf);
}

@@ -7773,6 +7789,19 @@ group_type group_classify(struct sched_g
return group_other;
}

+static void update_nohz_stats(struct rq *rq)
+{
+ unsigned int cpu = rq->cpu;
+
+ if (!cpumask_test_cpu(cpu, nohz.idle_cpus_mask))
+ return;
+
+ if (!time_after(jiffies, rq->last_blocked_load_update_tick))
+ return;
+
+ update_blocked_averages(cpu);
+}
+
/**
* update_sg_lb_stats - Update sched_group's statistics for load balancing.
* @env: The load balancing environment.
@@ -7795,6 +7824,9 @@ static inline void update_sg_lb_stats(st
for_each_cpu_and(i, sched_group_span(group), env->cpus) {
struct rq *rq = cpu_rq(i);

+ if (env->flags & LBF_NOHZ_STATS)
+ update_nohz_stats(rq);
+
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i, load_idx);
@@ -7950,6 +7982,15 @@ static inline void update_sd_lb_stats(st
if (child && child->flags & SD_PREFER_SIBLING)
prefer_sibling = 1;

+#ifdef CONFIG_NO_HZ_COMMON
+ if (env->idle == CPU_NEWLY_IDLE) {
+ env->flags |= LBF_NOHZ_STATS;
+
+ if (cpumask_subset(nohz.idle_cpus_mask, sched_domain_span(env->sd)))
+ nohz.next_stats = jiffies + msecs_to_jiffies(LOAD_AVG_PERIOD);
+ }
+#endif
+
load_idx = get_sd_load_idx(env->sd, env->idle);

do {
@@ -8968,12 +9009,6 @@ static inline int on_null_domain(struct
* needed, they will kick the idle load balancer, which then does idle
* load balancing for all the idle CPUs.
*/
-static struct {
- cpumask_var_t idle_cpus_mask;
- atomic_t nr_cpus;
- unsigned long next_balance; /* in jiffy units */
- unsigned long next_stats;
-} nohz ____cacheline_aligned;

static inline int find_new_ilb(void)
{
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -722,6 +722,7 @@ struct rq {
#ifdef CONFIG_NO_HZ_COMMON
#ifdef CONFIG_SMP
unsigned long last_load_update_tick;
+ unsigned long last_blocked_load_update_tick;
#endif /* CONFIG_SMP */
atomic_t nohz_flags;
#endif /* CONFIG_NO_HZ_COMMON */

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