sched/fair: Update blocked load from NEWIDLE

Since we already iterate CPUs looking for work on NEWIDLE, use this
iteration to age the blocked load. If the domain for which this is
done completely spand the idle set, we can push the ILB based aging
forward.

Suggested-by: Brendan Jackman <brendan.jackman@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 69c9a6b07b61cc76c2fda415f2b988e226995bd8..8a10a2ce30a4920dd96ef57df0f2a33f9922cc89 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6074,6 +6074,7 @@ 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
 #endif /* CONFIG_SMP */

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d8693fa9e7c5ad6206d6a6e81c5c78ae4559679a..85232dad89c90d2ac8e8c276ad500f2f444b5974 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5376,6 +5376,14 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
        }
        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 */
 
 /**
@@ -7022,6 +7030,7 @@ 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;
@@ -7460,6 +7469,10 @@ static void update_blocked_averages(int cpu)
                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);
 }
 
@@ -7519,6 +7532,9 @@ static inline void update_blocked_averages(int cpu)
        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);
 }
 
@@ -7853,6 +7869,21 @@ group_type group_classify(struct sched_group *group,
        return group_other;
 }
 
+static void update_nohz_stats(struct rq *rq)
+{
+#ifdef CONFIG_NO_HZ_COMMON
+       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);
+#endif
+}
+
 /**
  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
  * @env: The load balancing environment.
@@ -7875,6 +7906,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
        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);
@@ -8030,6 +8064,15 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd
        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 {
@@ -9049,12 +9092,6 @@ static inline int on_null_domain(struct rq *rq)
  *   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)
 {

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5295f274053b5c9e0a730f49ddfcff0e8d192ac5..21381d276709b4363fb89c66b5abef7bdc10bb9a 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -762,6 +762,7 @@ 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 */