[PATCH V3 1/4] sched/numa: Apply the scan delay to every new vma

[Raghavendra K T <raghavendra.kt@xxxxxxx>]

From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

Currently whenever a new task is created we wait for
sysctl_numa_balancing_scan_delay to avoid unnessary scanning
overhead. Extend the same logic to new or very short-lived VMAs.

(Raghavendra: Add initialization in vm_area_dup())

Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxx>
---
 include/linux/mm.h       | 16 ++++++++++++++++
 include/linux/mm_types.h |  7 +++++++
 kernel/fork.c            |  2 ++
 kernel/sched/fair.c      | 19 +++++++++++++++++++
 4 files changed, 44 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 974ccca609d2..41cc8997d4e5 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -29,6 +29,7 @@
 #include <linux/pgtable.h>
 #include <linux/kasan.h>
 #include <linux/memremap.h>
+#include <linux/slab.h>
 
 struct mempolicy;
 struct anon_vma;
@@ -611,6 +612,20 @@ struct vm_operations_struct {
 					  unsigned long addr);
 };
 
+#ifdef CONFIG_NUMA_BALANCING
+static inline void vma_numab_state_init(struct vm_area_struct *vma)
+{
+	vma->numab_state = NULL;
+}
+static inline void vma_numab_state_free(struct vm_area_struct *vma)
+{
+	kfree(vma->numab_state);
+}
+#else
+static inline void vma_numab_state_init(struct vm_area_struct *vma) {}
+static inline void vma_numab_state_free(struct vm_area_struct *vma) {}
+#endif /* CONFIG_NUMA_BALANCING */
+
 static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 {
 	static const struct vm_operations_struct dummy_vm_ops = {};
@@ -619,6 +634,7 @@ static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
 	vma->vm_mm = mm;
 	vma->vm_ops = &dummy_vm_ops;
 	INIT_LIST_HEAD(&vma->anon_vma_chain);
+	vma_numab_state_init(vma);
 }
 
 static inline void vma_set_anonymous(struct vm_area_struct *vma)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 500e536796ca..a4a1093870d3 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -435,6 +435,10 @@ struct anon_vma_name {
 	char name[];
 };
 
+struct vma_numab_state {
+	unsigned long next_scan;
+};
+
 /*
  * This struct describes a virtual memory area. There is one of these
  * per VM-area/task. A VM area is any part of the process virtual memory
@@ -504,6 +508,9 @@ struct vm_area_struct {
 #endif
 #ifdef CONFIG_NUMA
 	struct mempolicy *vm_policy;	/* NUMA policy for the VMA */
+#endif
+#ifdef CONFIG_NUMA_BALANCING
+	struct vma_numab_state *numab_state;	/* NUMA Balancing state */
 #endif
 	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 } __randomize_layout;
diff --git a/kernel/fork.c b/kernel/fork.c
index 08969f5aa38d..6c19a3305990 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -474,6 +474,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 		 */
 		*new = data_race(*orig);
 		INIT_LIST_HEAD(&new->anon_vma_chain);
+		vma_numab_state_init(new);
 		dup_anon_vma_name(orig, new);
 	}
 	return new;
@@ -481,6 +482,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 
 void vm_area_free(struct vm_area_struct *vma)
 {
+	vma_numab_state_free(vma);
 	free_anon_vma_name(vma);
 	kmem_cache_free(vm_area_cachep, vma);
 }
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e4a0b8bd941c..e39c36e71cec 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3015,6 +3015,25 @@ static void task_numa_work(struct callback_head *work)
 		if (!vma_is_accessible(vma))
 			continue;
 
+		/* Initialise new per-VMA NUMAB state. */
+		if (!vma->numab_state) {
+			vma->numab_state = kzalloc(sizeof(struct vma_numab_state),
+				GFP_KERNEL);
+			if (!vma->numab_state)
+				continue;
+
+			vma->numab_state->next_scan = now +
+				msecs_to_jiffies(sysctl_numa_balancing_scan_delay);
+		}
+
+		/*
+		 * Scanning the VMA's of short lived tasks add more overhead. So
+		 * delay the scan for new VMAs.
+		 */
+		if (mm->numa_scan_seq && time_before(jiffies,
+						vma->numab_state->next_scan))
+			continue;
+
 		do {
 			start = max(start, vma->vm_start);
 			end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
-- 
2.34.1