[PATCH 4/5] mm/vmalloc.c: improve performance for pcpu_get_vm_areas()

[zijun_hu <zijun_hu@zoho.com>]

From: zijun_hu <zijun_hu@htc.com>

improve performance for pcpu_get_vm_areas() in below aspects
 - reduce the counter of vmap_areas overlay checkup loop to half
 - find the previous or next one of a vamp_area by list_head but rbtree

Signed-off-by: zijun_hu <zijun_hu@htc.com>
---
 include/linux/list.h | 11 +++++++++++
 mm/internal.h        |  6 ++++++
 mm/memblock.c        | 10 ++--------
 mm/vmalloc.c         | 55 +++++++++++++++++++++++++++++++++-------------------
 4 files changed, 54 insertions(+), 28 deletions(-)

diff --git a/include/linux/list.h b/include/linux/list.h
index 5183138..23c3081 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -181,6 +181,17 @@ static inline int list_is_last(const struct list_head *list,
 }
 
 /**
+ * list_is_first - tests whether @list is the first entry in list @head
+ * @list: the entry to test
+ * @head: the head of the list
+ */
+static inline int list_is_first(const struct list_head *list,
+				const struct list_head *head)
+{
+	return list->prev == head;
+}
+
+/**
  * list_empty - tests whether a list is empty
  * @head: the list to test.
  */
diff --git a/mm/internal.h b/mm/internal.h
index 1501304..abbff7c 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -71,6 +71,12 @@ static inline void set_page_refcounted(struct page *page)
 	set_page_count(page, 1);
 }
 
+/**
+ * check whether range [@s0, @e0) has intersection with [@s1, @e1)
+ */
+#define is_range_overlay(s0, e0, s1, e1) \
+	(((s1) >= (e0) || (s0) >= (e1)) ? false : true)
+
 extern unsigned long highest_memmap_pfn;
 
 /*
diff --git a/mm/memblock.c b/mm/memblock.c
index 483197e..b4c7d7c 100644
--- a/mm/memblock.c
+++ b/mm/memblock.c
@@ -85,20 +85,14 @@ static inline phys_addr_t memblock_cap_size(phys_addr_t base, phys_addr_t *size)
 /*
  * Address comparison utilities
  */
-static unsigned long __init_memblock memblock_addrs_overlap(phys_addr_t base1, phys_addr_t size1,
-				       phys_addr_t base2, phys_addr_t size2)
-{
-	return ((base1 < (base2 + size2)) && (base2 < (base1 + size1)));
-}
-
 bool __init_memblock memblock_overlaps_region(struct memblock_type *type,
 					phys_addr_t base, phys_addr_t size)
 {
 	unsigned long i;
 
 	for (i = 0; i < type->cnt; i++)
-		if (memblock_addrs_overlap(base, size, type->regions[i].base,
-					   type->regions[i].size))
+		if (is_range_overlay(base, base + size, type->regions[i].base,
+				type->regions[i].base + type->regions[i].size))
 			break;
 	return i < type->cnt;
 }
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 2804224..5eeecc3 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -291,6 +291,22 @@ static unsigned long cached_align;
 
 static unsigned long vmap_area_pcpu_hole;
 
+static inline struct vmap_area *next_vmap_area(struct vmap_area *va)
+{
+	if (list_is_last(&va->list, &vmap_area_list))
+		return  NULL;
+	else
+		return list_next_entry(va, list);
+}
+
+static inline struct vmap_area *prev_vmap_area(struct vmap_area *va)
+{
+	if (list_is_first(&va->list, &vmap_area_list))
+		return  NULL;
+	else
+		return list_prev_entry(va, list);
+}
+
 static struct vmap_area *__find_vmap_area(unsigned long addr)
 {
 	struct rb_node *n = vmap_area_root.rb_node;
@@ -1112,7 +1128,7 @@ void vm_unmap_ram(const void *mem, unsigned int count)
 
 	BUG_ON(!addr);
 	BUG_ON(addr < VMALLOC_START);
-	BUG_ON(addr > VMALLOC_END);
+	BUG_ON(addr >= VMALLOC_END);
 	BUG_ON(!PAGE_ALIGNED(addr));
 
 	debug_check_no_locks_freed(mem, size);
@@ -2296,10 +2312,6 @@ void free_vm_area(struct vm_struct *area)
 EXPORT_SYMBOL_GPL(free_vm_area);
 
 #ifdef CONFIG_SMP
-static struct vmap_area *node_to_va(struct rb_node *n)
-{
-	return n ? rb_entry(n, struct vmap_area, rb_node) : NULL;
-}
 
 /**
  * pvm_find_next_prev - find the next and prev vmap_area surrounding @end
@@ -2335,10 +2347,10 @@ static bool pvm_find_next_prev(unsigned long end,
 
 	if (va->va_end > end) {
 		*pnext = va;
-		*pprev = node_to_va(rb_prev(&(*pnext)->rb_node));
+		*pprev = prev_vmap_area(va);
 	} else {
 		*pprev = va;
-		*pnext = node_to_va(rb_next(&(*pprev)->rb_node));
+		*pnext = next_vmap_area(va);
 	}
 	return true;
 }
@@ -2373,7 +2385,7 @@ static unsigned long pvm_determine_end(struct vmap_area **pnext,
 
 	while (*pprev && (*pprev)->va_end > addr) {
 		*pnext = *pprev;
-		*pprev = node_to_va(rb_prev(&(*pnext)->rb_node));
+		*pprev = prev_vmap_area(*pnext);
 	}
 
 	return addr;
@@ -2413,31 +2425,34 @@ struct vm_struct **pcpu_get_vm_areas(const unsigned long *offsets,
 	struct vm_struct **vms;
 	int area, area2, last_area, term_area;
 	unsigned long base, start, end, last_end;
+	unsigned long start2, end2;
 	bool purged = false;
 
 	/* verify parameters and allocate data structures */
+	if (nr_vms < 1)
+		return NULL;
 	BUG_ON(offset_in_page(align) || !is_power_of_2(align));
-	for (last_area = 0, area = 0; area < nr_vms; area++) {
+
+	last_area = nr_vms - 1;
+	BUG_ON(!IS_ALIGNED(offsets[last_area], align));
+	BUG_ON(!IS_ALIGNED(sizes[last_area], align));
+	for (area = 0; area < nr_vms - 1; area++) {
 		start = offsets[area];
 		end = start + sizes[area];
 
 		/* is everything aligned properly? */
-		BUG_ON(!IS_ALIGNED(offsets[area], align));
-		BUG_ON(!IS_ALIGNED(sizes[area], align));
+		BUG_ON(!IS_ALIGNED(start, align));
+		BUG_ON(!IS_ALIGNED(end, align));
 
 		/* detect the area with the highest address */
 		if (start > offsets[last_area])
 			last_area = area;
 
-		for (area2 = 0; area2 < nr_vms; area2++) {
-			unsigned long start2 = offsets[area2];
-			unsigned long end2 = start2 + sizes[area2];
-
-			if (area2 == area)
-				continue;
+		for (area2 = area + 1; area2 < nr_vms; area2++) {
+			start2 = offsets[area2];
+			end2 = start2 + sizes[area2];
 
-			BUG_ON(start2 >= start && start2 < end);
-			BUG_ON(end2 <= end && end2 > start);
+			BUG_ON(is_range_overlay(start, end, start2, end2));
 		}
 	}
 	last_end = offsets[last_area] + sizes[last_area];
@@ -2507,7 +2522,7 @@ retry:
 		 */
 		if (prev && prev->va_end > base + start)  {
 			next = prev;
-			prev = node_to_va(rb_prev(&next->rb_node));
+			prev = prev_vmap_area(next);
 			base = pvm_determine_end(&next, &prev, align) - end;
 			term_area = area;
 			continue;
-- 
1.9.1

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