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Date: Thu, 4 Sep 2014 20:30:56 +0400
From: klamm@...dex-team.ru
To: peterz@...radead.org, mingo@...hat.com,
linux-kernel@...r.kernel.org
Cc: stfomichev@...dex-team.ru, Roman Gushchin <klamm@...dex-team.ru>
Subject: [PATCH 10/19] smart: smart gathering
From: Roman Gushchin <klamm@...dex-team.ru>
Previous patch denies starting new CFS tasks on a core with running rt
tasks. The problem still exists if there are already running CFS tasks
at the moment rt task starts.
This patch introduces smart gathering - migration of running CFS tasks
from all other CPUs to the CPU with rt task.
Signed-off-by: Roman Gushchin <klamm@...dex-team.ru>
---
kernel/sched/core.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 14 ++++++++
kernel/sysctl.c | 1 +
3 files changed, 113 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 9d888610c..5954f48 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2753,6 +2753,8 @@ void scheduler_tick(void)
curr->sched_class->task_tick(rq, curr, 0);
raw_spin_unlock(&rq->lock);
+ smart_tick(cpu);
+
perf_event_task_tick();
#ifdef CONFIG_SMP
@@ -4921,6 +4923,97 @@ static int migration_cpu_stop(void *data)
}
#ifdef CONFIG_SMART
+
+DEFINE_PER_CPU_SHARED_ALIGNED(struct smart_gathering, smart_gathering_data);
+
+static int smart_gathering_cpu_stop(void *data)
+{
+ int this_cpu = smp_processor_id();
+ int dest_cpu = cpu_core_id(this_cpu);
+ struct rq *rq = cpu_rq(this_cpu);
+ struct task_struct *next;
+ struct smart_gathering *sg;
+ unsigned long flags;
+ int ret;
+ int iter;
+
+ WARN_ON(this_cpu == dest_cpu);
+
+ raw_spin_lock_irqsave(&rq->lock, flags);
+ for (iter = 0; iter < rq->cfs.h_nr_running; iter++) {
+ next = fair_sched_class.pick_next_task(rq);
+ if (!next)
+ break;
+ next->sched_class->put_prev_task(rq, next);
+
+ if (!cpumask_test_cpu(dest_cpu, tsk_cpus_allowed(next)) ||
+ !cpu_online(dest_cpu))
+ break;
+
+ raw_spin_unlock(&rq->lock);
+ ret = __migrate_task(next, this_cpu, dest_cpu);
+ raw_spin_lock(&rq->lock);
+
+ if (!ret)
+ break;
+ }
+ raw_spin_unlock_irqrestore(&rq->lock, flags);
+
+ sg = &smart_gathering_data(this_cpu);
+ spin_lock_irqsave(&sg->lock, flags);
+ WARN_ON(!sg->gather);
+ sg->gather = 0;
+ spin_unlock_irqrestore(&sg->lock, flags);
+
+ return 0;
+}
+
+void smart_tick(int cpu)
+{
+ unsigned long flags;
+ struct smart_gathering *sg;
+ int gather = 0;
+ struct rq *rq;
+ int core;
+ struct task_struct *curr;
+
+ if (idle_cpu(cpu) || !smart_enabled() ||
+ !static_key_true(&smart_cfs_gather))
+ return;
+
+ rcu_read_lock();
+
+ core = cpu_core_id(cpu);
+ if (cpu != core) {
+ rq = cpu_rq(core);
+ curr = rq->curr;
+ if (rt_task(curr) && curr->mm)
+ gather = 1;
+
+ rq = cpu_rq(cpu);
+ curr = rq->curr;
+ if (rt_task(curr))
+ gather = 0;
+ }
+
+ if (gather) {
+ sg = &smart_gathering_data(cpu);
+
+ spin_lock_irqsave(&sg->lock, flags);
+ if (sg->gather)
+ gather = 0;
+ else
+ sg->gather = 1;
+ spin_unlock_irqrestore(&sg->lock, flags);
+ }
+
+ rcu_read_unlock();
+
+ if (gather)
+ stop_one_cpu_nowait(cpu, smart_gathering_cpu_stop, NULL,
+ &sg->work);
+}
+
int smart_migrate_task(struct task_struct *p, int prev_cpu,
int dest_cpu)
{
@@ -7093,6 +7186,11 @@ void __init sched_init(void)
#endif
init_rq_hrtick(rq);
atomic_set(&rq->nr_iowait, 0);
+
+#ifdef CONFIG_SMART
+ spin_lock_init(&smart_gathering_data(i).lock);
+ smart_gathering_data(i).gather = 0;
+#endif
}
set_load_weight(&init_task);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index c7c1cdc..80d202e 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1394,11 +1394,19 @@ struct smart_node_data {
atomic_t nr_rt_running;
} ____cacheline_aligned_in_smp;
+struct smart_gathering {
+ spinlock_t lock;
+ int gather;
+ struct cpu_stop_work work;
+};
+
extern struct static_key __smart_initialized;
extern struct static_key __smart_enabled;
+extern struct static_key smart_cfs_gather;
extern struct static_key smart_cfs_throttle;
DECLARE_PER_CPU_SHARED_ALIGNED(struct smart_core_data, smart_core_data);
+DECLARE_PER_CPU_SHARED_ALIGNED(struct smart_gathering, smart_gathering_data);
extern struct smart_node_data smart_node_data[MAX_NUMNODES];
static inline int cpu_core_id(int cpu)
@@ -1408,6 +1416,7 @@ static inline int cpu_core_id(int cpu)
#define smart_data(cpu) per_cpu(smart_core_data, cpu_core_id(cpu))
#define smart_node_ptr(cpu) smart_node_data[cpu_to_node(cpu)]
+#define smart_gathering_data(cpu) per_cpu(smart_gathering_data, cpu)
static inline bool smart_enabled(void)
{
@@ -1586,6 +1595,7 @@ static inline void reset_smart_score(struct sched_rt_entity *rt_se)
atomic_set(&rt_se->smart_score, 0);
}
+void smart_tick(int cpu);
int smart_migrate_task(struct task_struct *p, int prev_cpu, int dest_cpu);
void build_smart_topology(void);
@@ -1620,4 +1630,8 @@ static inline bool cpu_allowed_for_cfs(int cpu)
return true;
}
+static inline void smart_tick(int cpu)
+{
+}
+
#endif /* CONFIG_SMART */
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 7ee22ef..a1e71e9 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -176,6 +176,7 @@ extern int no_unaligned_warning;
#endif
#ifdef CONFIG_SMART
+struct static_key smart_cfs_gather = STATIC_KEY_INIT_TRUE;
struct static_key smart_cfs_throttle = STATIC_KEY_INIT_TRUE;
#endif
--
1.9.3
--
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