From: Peter Zijlstra <pet...@infradead.org>
Introduce the basic infrastructure to have a core wide rq->lock.
Tested-by: Julien Desfossez <jdesfos...@digitalocean.com>
Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Signed-off-by: Julien Desfossez <jdesfos...@digitalocean.com>
Signed-off-by: Vineeth Remanan Pillai <virem...@linux.microsoft.com>
Signed-off-by: Joel Fernandes (Google) <j...@joelfernandes.org>
---
kernel/Kconfig.preempt | 5 ++
kernel/sched/core.c | 108 +++++++++++++++++++++++++++++++++++++++++
kernel/sched/sched.h | 31 ++++++++++++
3 files changed, 144 insertions(+)
diff --git a/kernel/Kconfig.preempt b/kernel/Kconfig.preempt
index bf82259cff96..6d8be4630bd6 100644
--- a/kernel/Kconfig.preempt
+++ b/kernel/Kconfig.preempt
@@ -80,3 +80,8 @@ config PREEMPT_COUNT
config PREEMPTION
bool
select PREEMPT_COUNT
+
+config SCHED_CORE
+ bool "Core Scheduling for SMT"
+ default y
+ depends on SCHED_SMT
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index db5cc05a68bc..6d88bc9a6818 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -74,6 +74,70 @@ unsigned int sysctl_sched_rt_period = 1000000;
__read_mostly int scheduler_running;
+#ifdef CONFIG_SCHED_CORE
+
+DEFINE_STATIC_KEY_FALSE(__sched_core_enabled);
+
+/*
+ * The static-key + stop-machine variable are needed such that:
+ *
+ * spin_lock(rq_lockp(rq));
+ * ...
+ * spin_unlock(rq_lockp(rq));
+ *
+ * ends up locking and unlocking the _same_ lock, and all CPUs
+ * always agree on what rq has what lock.
+ *
+ * XXX entirely possible to selectively enable cores, don't bother for now.
+ */
+static int __sched_core_stopper(void *data)
+{
+ bool enabled = !!(unsigned long)data;
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ cpu_rq(cpu)->core_enabled = enabled;
+
+ return 0;
+}
+
+static DEFINE_MUTEX(sched_core_mutex);
+static int sched_core_count;
+
+static void __sched_core_enable(void)
+{
+ // XXX verify there are no cookie tasks (yet)
+
+ static_branch_enable(&__sched_core_enabled);
+ stop_machine(__sched_core_stopper, (void *)true, NULL);
+}
+
+static void __sched_core_disable(void)
+{
+ // XXX verify there are no cookie tasks (left)
+
+ stop_machine(__sched_core_stopper, (void *)false, NULL);
+ static_branch_disable(&__sched_core_enabled);
+}
+
+void sched_core_get(void)
+{
+ mutex_lock(&sched_core_mutex);
+ if (!sched_core_count++)
+ __sched_core_enable();
+ mutex_unlock(&sched_core_mutex);
+}
+
+void sched_core_put(void)
+{
+ mutex_lock(&sched_core_mutex);
+ if (!--sched_core_count)
+ __sched_core_disable();
+ mutex_unlock(&sched_core_mutex);
+}
+
+#endif /* CONFIG_SCHED_CORE */
+
/*
* part of the period that we allow rt tasks to run in us.
* default: 0.95s
@@ -4859,6 +4923,42 @@ pick_next_task(struct rq *rq, struct task_struct *prev,
struct rq_flags *rf)
BUG();
}
+#ifdef CONFIG_SCHED_CORE
+
+static inline void sched_core_cpu_starting(unsigned int cpu)
+{
+ const struct cpumask *smt_mask = cpu_smt_mask(cpu);
+ struct rq *rq, *core_rq = NULL;
+ int i;
+
+ core_rq = cpu_rq(cpu)->core;
+
+ if (!core_rq) {
+ for_each_cpu(i, smt_mask) {
+ rq = cpu_rq(i);
+ if (rq->core && rq->core == rq)
+ core_rq = rq;
+ }
+
+ if (!core_rq)
+ core_rq = cpu_rq(cpu);
+
+ for_each_cpu(i, smt_mask) {
+ rq = cpu_rq(i);
+
+ WARN_ON_ONCE(rq->core && rq->core != core_rq);
+ rq->core = core_rq;
+ }
+ }
+
+ printk("core: %d -> %d\n", cpu, cpu_of(core_rq));
+}
+#else /* !CONFIG_SCHED_CORE */
+
+static inline void sched_core_cpu_starting(unsigned int cpu) {}
+
+#endif /* CONFIG_SCHED_CORE */
+
/*
* __schedule() is the main scheduler function.
*
@@ -7484,6 +7584,9 @@ static void sched_rq_cpu_starting(unsigned int cpu)
int sched_cpu_starting(unsigned int cpu)
{
+
+ sched_core_cpu_starting(cpu);
+
sched_rq_cpu_starting(cpu);
sched_tick_start(cpu);
return 0;
@@ -7747,6 +7850,11 @@ void __init sched_init(void)
#endif /* CONFIG_SMP */
hrtick_rq_init(rq);
atomic_set(&rq->nr_iowait, 0);
+
+#ifdef CONFIG_SCHED_CORE
+ rq->core = NULL;
+ rq->core_enabled = 0;
+#endif
}
set_load_weight(&init_task, false);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 5a0dd2b312aa..0dfccf988998 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1061,6 +1061,12 @@ struct rq {
#endif
unsigned int push_busy;
struct cpu_stop_work push_work;
+
+#ifdef CONFIG_SCHED_CORE
+ /* per rq */
+ struct rq *core;
+ unsigned int core_enabled;
+#endif
};
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -1099,11 +1105,36 @@ static inline bool is_migration_disabled(struct
task_struct *p)
#endif
}
+#ifdef CONFIG_SCHED_CORE
+DECLARE_STATIC_KEY_FALSE(__sched_core_enabled);
+
+static inline bool sched_core_enabled(struct rq *rq)
+{
+ return static_branch_unlikely(&__sched_core_enabled) &&
rq->core_enabled;
+}
+
+static inline raw_spinlock_t *rq_lockp(struct rq *rq)
+{
+ if (sched_core_enabled(rq))
+ return &rq->core->__lock;
+
+ return &rq->__lock;
+}
+
+#else /* !CONFIG_SCHED_CORE */
+
+static inline bool sched_core_enabled(struct rq *rq)
+{
+ return false;
+}
+
static inline raw_spinlock_t *rq_lockp(struct rq *rq)
{
return &rq->__lock;
}
+#endif /* CONFIG_SCHED_CORE */
+
#ifdef CONFIG_SCHED_SMT
extern void __update_idle_core(struct rq *rq);
--
2.29.2.299.gdc1121823c-goog
