[PATCH 39/43] sched: numa: Introduce per-mm and per-task structures

[Mel Gorman]

NOTE: This is heavily based on "autonuma: CPU follows memory algorithm"
	and "autonuma: mm_autonuma and task_autonuma data structures"

At the most basic level, any placement policy is going to make some
sort of smart decision based on per-mm and per-task statistics. This
patch simply introduces the structures with basic fault statistics
that can be expaned upon or replaced later. It may be that a placement
policy can approximate without needing both structures in which case
they can be safely deleted later while still having a comparison point
to ensure the approximation is accurate.

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
 include/linux/mm_types.h |   26 ++++++++++++++++++++++++++
 include/linux/sched.h    |   18 ++++++++++++++++++
 kernel/fork.c            |   18 ++++++++++++++++++
 kernel/sched/core.c      |    3 +++
 kernel/sched/fair.c      |   25 ++++++++++++++++++++++++-
 kernel/sched/sched.h     |   14 ++++++++++++++
 6 files changed, 103 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6b478ff..9588a91 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -312,6 +312,29 @@ struct mm_rss_stat {
 	atomic_long_t count[NR_MM_COUNTERS];
 };
 
+#ifdef CONFIG_BALANCE_NUMA
+/*
+ * Per-mm structure that contains the NUMA memory placement statistics
+ * generated by pte_numa faults.
+ */
+struct mm_balancenuma {
+	/*
+	 * Number of pages that will trigger NUMA faults for this mm. Total
+	 * decays each time whether the home node should change to keep
+	 * track only of recent events
+	 */
+	unsigned long mm_numa_fault_tot;
+
+	/*
+	 * Number of pages that will trigger NUMA faults for each [nid].
+	 * Also decays.
+	 */
+	unsigned long mm_numa_fault[0];
+
+	/* do not add more variables here, the above array size is dynamic */
+};
+#endif /* CONFIG_BALANCE_NUMA */
+
 struct mm_struct {
 	struct vm_area_struct * mmap;		/* list of VMAs */
 	struct rb_root mm_rb;
@@ -415,6 +438,9 @@ struct mm_struct {
 
 	/* numa_scan_seq prevents two threads setting pte_numa */
 	int numa_scan_seq;
+
+	/* this is used by the scheduler and the page allocator */
+	struct mm_balancenuma *mm_balancenuma;
 #endif
 	struct uprobes_state uprobes_state;
 };
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 1cccfc3..7b6625a 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1188,6 +1188,23 @@ enum perf_event_task_context {
 	perf_nr_task_contexts,
 };
 
+#ifdef CONFIG_BALANCE_NUMA
+/*
+ * Per-task structure that contains the NUMA memory placement statistics
+ * generated by pte_numa faults. This structure is dynamically allocated
+ * when the first pte_numa fault is handled.
+ */
+struct task_balancenuma {
+	/* Total number of eligible pages that triggered NUMA faults */
+	unsigned long task_numa_fault_tot;
+
+	/* Number of pages that triggered NUMA faults for each [nid] */
+	unsigned long task_numa_fault[0];
+
+	/* do not add more variables here, the above array size is dynamic */
+};
+#endif /* CONFIG_BALANCE_NUMA */
+
 struct task_struct {
 	volatile long state;	/* -1 unrunnable, 0 runnable, >0 stopped */
 	void *stack;
@@ -1488,6 +1505,7 @@ struct task_struct {
 	unsigned int numa_scan_period;
 	u64 node_stamp;			/* migration stamp  */
 	struct callback_head numa_work;
+	struct task_balancenuma *task_balancenuma;
 #endif /* CONFIG_BALANCE_NUMA */
 
 	struct rcu_head rcu;
diff --git a/kernel/fork.c b/kernel/fork.c
index 8b20ab7..c8752f6 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -525,6 +525,20 @@ static void mm_init_aio(struct mm_struct *mm)
 #endif
 }
 
+#ifdef CONFIG_BALANCE_NUMA
+static inline void free_mm_balancenuma(struct mm_struct *mm)
+{
+	if (mm->mm_balancenuma)
+		kfree(mm->mm_balancenuma);
+
+	mm->mm_balancenuma = NULL;
+}
+#else
+static inline void free_mm_balancenuma(struct mm_struct *mm)
+{
+}
+#endif
+
 static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 {
 	atomic_set(&mm->mm_users, 1);
@@ -539,6 +553,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 	spin_lock_init(&mm->page_table_lock);
 	mm->free_area_cache = TASK_UNMAPPED_BASE;
 	mm->cached_hole_size = ~0UL;
+	mm->mm_balancenuma = NULL;
 	mm_init_aio(mm);
 	mm_init_owner(mm, p);
 
@@ -548,6 +563,7 @@ static struct mm_struct *mm_init(struct mm_struct *mm, struct task_struct *p)
 		return mm;
 	}
 
+	free_mm_balancenuma(mm);
 	free_mm(mm);
 	return NULL;
 }
@@ -597,6 +613,7 @@ void __mmdrop(struct mm_struct *mm)
 	destroy_context(mm);
 	mmu_notifier_mm_destroy(mm);
 	check_mm(mm);
+	free_mm_balancenuma(mm);
 	free_mm(mm);
 }
 EXPORT_SYMBOL_GPL(__mmdrop);
@@ -854,6 +871,7 @@ fail_nocontext:
 	 * If init_new_context() failed, we cannot use mmput() to free the mm
 	 * because it calls destroy_context()
 	 */
+	free_mm_balancenuma(mm);
 	mm_free_pgd(mm);
 	free_mm(mm);
 	return NULL;
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 3d9fc26..9472d5d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1543,6 +1543,7 @@ static void __sched_fork(struct task_struct *p)
 	p->node_stamp = 0ULL;
 	p->numa_scan_seq = p->mm ? p->mm->numa_scan_seq : 0;
 	p->numa_migrate_seq = p->mm ? p->mm->numa_scan_seq - 1 : 0;
+	p->task_balancenuma = NULL;
 	p->numa_scan_period = sysctl_balance_numa_scan_delay;
 	p->numa_work.next = &p->numa_work;
 #endif /* CONFIG_BALANCE_NUMA */
@@ -1787,6 +1788,8 @@ static void finish_task_switch(struct rq *rq, struct task_struct *prev)
 	if (mm)
 		mmdrop(mm);
 	if (unlikely(prev_state == TASK_DEAD)) {
+		free_task_balancenuma(prev);
+
 		/*
 		 * Remove function-return probe instances associated with this
 		 * task and put them back on the free list.
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 219158f..98c621c 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -854,7 +854,30 @@ void task_numa_fault(int node, int pages)
 {
 	struct task_struct *p = current;
 
-	/* FIXME: Allocate task-specific structure for placement policy here */
+	if (!p->task_balancenuma) {
+		int size = sizeof(struct task_balancenuma) +
+				(sizeof(unsigned long) * nr_node_ids);
+		p->task_balancenuma = kzalloc(size, GFP_KERNEL);
+		if (!p->task_balancenuma)
+			return;
+	}
+
+	if (!p->mm->mm_balancenuma) {
+		int size = sizeof(struct mm_balancenuma) +
+				(sizeof(unsigned long) * nr_node_ids);
+		p->mm->mm_balancenuma = kzalloc(size, GFP_KERNEL);
+		if (!p->mm->mm_balancenuma) {
+			kfree(p->task_balancenuma);
+			p->task_balancenuma = NULL;
+			return;
+		}
+	}
+
+	/* Record fault statistics */
+	p->task_balancenuma->task_numa_fault_tot++;
+	p->task_balancenuma->task_numa_fault[node]++;
+	p->mm->mm_balancenuma->mm_numa_fault_tot++;
+	p->mm->mm_balancenuma->mm_numa_fault[node]++;
 
 	/*
 	 * Assume that as faults occur that pages are getting properly placed
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3f0e5a1..92df3d4 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -502,6 +502,20 @@ DECLARE_PER_CPU(struct rq, runqueues);
 #define cpu_curr(cpu)		(cpu_rq(cpu)->curr)
 #define raw_rq()		(&__raw_get_cpu_var(runqueues))
 
+
+#ifdef CONFIG_BALANCE_NUMA
+static inline void free_task_balancenuma(struct task_struct *p)
+{
+	if (p->task_balancenuma)
+		kfree(p->task_balancenuma);
+	p->task_balancenuma = NULL;
+}
+#else
+static inline void free_task_balancenuma(struct task_struct *p)
+{
+}
+#endif /* CONFIG_BALANCE_NUMA */
+
 #ifdef CONFIG_SMP
 
 #define rcu_dereference_check_sched_domain(p) \
-- 
1.7.9.2

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